Clarify the caching of static assets under $site_path/static
Clarify the caching of static assets under $site_path/static

The header/footer/CSS are inlined into the host page, which is
never cached.  But $site_path/static uses a 5 minute age.

Signed-off-by: Shawn O. Pearce <f3ea74d906fa9fe97c1fef6bad9cb871485c7045@google.com>

quyixia/gerrit,WANdisco/gerrit,bootstraponline-archive/gerrit-mirror,qtproject/qtqa-gerrit,MerritCR/merrit,basilgor/gerrit,m1kah/gerrit-contributions,catrope/gerrit,MerritCR/merrit,sudosurootdev/gerrit,bpollack/gerrit,GerritCodeReview/gerrit-attic,ckamm/gerrit,renchaorevee/gerrit,thinkernel/gerrit,evanchueng/gerrit,gracefullife/gerrit,supriyantomaftuh/gerrit,bootstraponline-archive/gerrit-mirror,sudosurootdev/gerrit,Seinlin/gerrit,gcoders/gerrit,1yvT0s/gerrit,joshuawilson/merrit,basilgor/gerrit,sudosurootdev/gerrit,Seinlin/gerrit,m1kah/gerrit-contributions,Saulis/gerrit,Team-OctOS/host_gerrit,thesamet/gerrit,Distrotech/gerrit,thinkernel/gerrit,TonyChai24/test,MerritCR/merrit,evanchueng/gerrit,CandyShop/gerrit,skurfuerst/gerrit,joshuawilson/merrit,WANdisco/gerrit,skurfuerst/gerrit,gracefullife/gerrit,gerrit-review/gerrit,joshuawilson/merrit,pkdevbox/gerrit,TonyChai24/test,Team-OctOS/host_gerrit,midnightradio/gerrit,Seinlin/gerrit,quyixia/gerrit,catrope/gerrit,renchaorevee/gerrit,MerritCR/merrit,gcoders/gerrit,teamblueridge/gerrit,TonyChai24/test,ckamm/gerrit,dwhipstock/gerrit,Team-OctOS/host_gerrit,TonyChai24/test,Saulis/gerrit,hdost/gerrit,atdt/gerrit,Distrotech/gerrit,gerrit-review/gerrit,teamblueridge/gerrit,GerritCodeReview/gerrit,ashang/aaron-gerrit,gerrit-review/gerrit,renchaorevee/gerrit,zommarin/gerrit,GerritCodeReview/gerrit,Overruler/gerrit,cjh1/gerrit,MerritCR/merrit,qtproject/qtqa-gerrit,Overruler/gerrit,rtyley/mini-git-server,Distrotech/gerrit,ashang/aaron-gerrit,anminhsu/gerrit,MerritCR/merrit,teamblueridge/gerrit,joshuawilson/merrit,1yvT0s/gerrit,GerritCodeReview/gerrit,pkdevbox/gerrit,WANdisco/gerrit,dwhipstock/gerrit,Distrotech/gerrit,MerritCR/merrit,bootstraponline-archive/gerrit-mirror,zommarin/gerrit,sudosurootdev/gerrit,GerritCodeReview/gerrit,quyixia/gerrit,duboisf/gerrit,zommarin/gerrit,hdost/gerrit,jackminicloud/test,thesamet/gerrit,gcoders/gerrit,Seinlin/gerrit,dwhipstock/gerrit,austinchic/Gerrit,GerritCodeReview/gerrit-attic,jackminicloud/test,netroby/gerrit,anminhsu/gerrit,joshuawilson/merrit,pkdevbox/gerrit,basilgor/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,midnightradio/gerrit,m1kah/gerrit-contributions,midnightradio/gerrit,austinchic/Gerrit,thinkernel/gerrit,thesamet/gerrit,jeblair/gerrit,joshuawilson/merrit,makholm/gerrit-ceremony,netroby/gerrit,pkdevbox/gerrit,TonyChai24/test,Overruler/gerrit,bpollack/gerrit,atdt/gerrit,gcoders/gerrit,WANdisco/gerrit,netroby/gerrit,GerritCodeReview/gerrit,Overruler/gerrit,anminhsu/gerrit,qtproject/qtqa-gerrit,thesamet/gerrit,anminhsu/gerrit,thesamet/gerrit,gerrit-review/gerrit,quyixia/gerrit,joshuawilson/merrit,TonyChai24/test,supriyantomaftuh/gerrit,CandyShop/gerrit,ckamm/gerrit,supriyantomaftuh/gerrit,gerrit-review/gerrit,atdt/gerrit,Saulis/gerrit,renchaorevee/gerrit,gracefullife/gerrit,supriyantomaftuh/gerrit,supriyantomaftuh/gerrit,jackminicloud/test,gracefullife/gerrit,dwhipstock/gerrit,thinkernel/gerrit,supriyantomaftuh/gerrit,ashang/aaron-gerrit,midnightradio/gerrit,austinchic/Gerrit,anminhsu/gerrit,basilgor/gerrit,hdost/gerrit,keerath/gerrit_newssh,Overruler/gerrit,netroby/gerrit,hdost/gerrit,netroby/gerrit,duboisf/gerrit,qtproject/qtqa-gerrit,TonyChai24/test,jackminicloud/test,jeblair/gerrit,Saulis/gerrit,keerath/gerrit_newssh,gracefullife/gerrit,dwhipstock/gerrit,catrope/gerrit,CandyShop/gerrit,gcoders/gerrit,duboisf/gerrit,skurfuerst/gerrit,WANdisco/gerrit,sudosurootdev/gerrit,gcoders/gerrit,Team-OctOS/host_gerrit,Saulis/gerrit,gcoders/gerrit,GerritCodeReview/gerrit-attic,CandyShop/gerrit,anminhsu/gerrit,bootstraponline-archive/gerrit-mirror,jackminicloud/test,quyixia/gerrit,GerritCodeReview/gerrit,cjh1/gerrit,quyixia/gerrit,cjh1/gerrit,ckamm/gerrit,makholm/gerrit-ceremony,basilgor/gerrit,thinkernel/gerrit,keerath/gerrit_newssh,atdt/gerrit,WANdisco/gerrit,Overruler/gerrit,hdost/gerrit,evanchueng/gerrit,1yvT0s/gerrit,thesamet/gerrit,qtproject/qtqa-gerrit,teamblueridge/gerrit,pkdevbox/gerrit,bpollack/gerrit,Seinlin/gerrit,netroby/gerrit,Team-OctOS/host_gerrit,thinkernel/gerrit,dwhipstock/gerrit,supriyantomaftuh/gerrit,austinchic/Gerrit,anminhsu/gerrit,hdost/gerrit,hdost/gerrit,jeblair/gerrit,zommarin/gerrit,pkdevbox/gerrit,ashang/aaron-gerrit,gerrit-review/gerrit,evanchueng/gerrit,renchaorevee/gerrit,ckamm/gerrit,Team-OctOS/host_gerrit,cjh1/gerrit,Distrotech/gerrit,1yvT0s/gerrit,Distrotech/gerrit,skurfuerst/gerrit,Seinlin/gerrit,zommarin/gerrit,atdt/gerrit,renchaorevee/gerrit,ashang/aaron-gerrit,1yvT0s/gerrit,MerritCR/merrit,teamblueridge/gerrit,Saulis/gerrit,CandyShop/gerrit,renchaorevee/gerrit,jeblair/gerrit,bpollack/gerrit,makholm/gerrit-ceremony,GerritCodeReview/gerrit,bootstraponline-archive/gerrit-mirror,bpollack/gerrit,Distrotech/gerrit,bpollack/gerrit,netroby/gerrit,jackminicloud/test,catrope/gerrit,dwhipstock/gerrit,bootstraponline-archive/gerrit-mirror,duboisf/gerrit,evanchueng/gerrit,rtyley/mini-git-server,thinkernel/gerrit,Seinlin/gerrit,joshuawilson/merrit,keerath/gerrit_newssh,keerath/gerrit_newssh,thesamet/gerrit,midnightradio/gerrit,m1kah/gerrit-contributions,makholm/gerrit-ceremony,jackminicloud/test,WANdisco/gerrit,Team-OctOS/host_gerrit,midnightradio/gerrit,qtproject/qtqa-gerrit,quyixia/gerrit,gerrit-review/gerrit,pkdevbox/gerrit