Add some info to gitweb access control docs.
Add some info to gitweb access control docs.

In order for a user to be allowed to view any gitweb information about a
repository, they must have read access to all references. Now this fact
is documented.

Change-Id: I8bb738678af89599318bbe114e35b2a63fc09f6f

WANdisco/gerrit,Distrotech/gerrit,Team-OctOS/host_gerrit,netroby/gerrit,MerritCR/merrit,quyixia/gerrit,gerrit-review/gerrit,gcoders/gerrit,Team-OctOS/host_gerrit,Seinlin/gerrit,thesamet/gerrit,thinkernel/gerrit,gcoders/gerrit,jackminicloud/test,Saulis/gerrit,TonyChai24/test,MerritCR/merrit,thinkernel/gerrit,WANdisco/gerrit,MerritCR/merrit,gerrit-review/gerrit,gcoders/gerrit,hdost/gerrit,hdost/gerrit,WANdisco/gerrit,gerrit-review/gerrit,dwhipstock/gerrit,midnightradio/gerrit,anminhsu/gerrit,jackminicloud/test,bpollack/gerrit,gerrit-review/gerrit,dwhipstock/gerrit,TonyChai24/test,joshuawilson/merrit,bootstraponline-archive/gerrit-mirror,dwhipstock/gerrit,supriyantomaftuh/gerrit,hdost/gerrit,midnightradio/gerrit,joshuawilson/merrit,GerritCodeReview/gerrit,Team-OctOS/host_gerrit,bpollack/gerrit,netroby/gerrit,MerritCR/merrit,midnightradio/gerrit,thinkernel/gerrit,GerritCodeReview/gerrit,pkdevbox/gerrit,MerritCR/merrit,joshuawilson/merrit,netroby/gerrit,quyixia/gerrit,GerritCodeReview/gerrit,renchaorevee/gerrit,Saulis/gerrit,bootstraponline-archive/gerrit-mirror,jackminicloud/test,jackminicloud/test,Distrotech/gerrit,quyixia/gerrit,Seinlin/gerrit,MerritCR/merrit,hdost/gerrit,gerrit-review/gerrit,supriyantomaftuh/gerrit,pkdevbox/gerrit,quyixia/gerrit,pkdevbox/gerrit,hdost/gerrit,GerritCodeReview/gerrit,Seinlin/gerrit,GerritCodeReview/gerrit,supriyantomaftuh/gerrit,anminhsu/gerrit,jackminicloud/test,Team-OctOS/host_gerrit,bpollack/gerrit,Saulis/gerrit,pkdevbox/gerrit,renchaorevee/gerrit,thesamet/gerrit,gcoders/gerrit,WANdisco/gerrit,Distrotech/gerrit,joshuawilson/merrit,TonyChai24/test,dwhipstock/gerrit,supriyantomaftuh/gerrit,netroby/gerrit,joshuawilson/merrit,netroby/gerrit,qtproject/qtqa-gerrit,Seinlin/gerrit,Distrotech/gerrit,pkdevbox/gerrit,supriyantomaftuh/gerrit,thinkernel/gerrit,Saulis/gerrit,jackminicloud/test,renchaorevee/gerrit,bpollack/gerrit,Team-OctOS/host_gerrit,dwhipstock/gerrit,midnightradio/gerrit,GerritCodeReview/gerrit,MerritCR/merrit,thesamet/gerrit,qtproject/qtqa-gerrit,anminhsu/gerrit,joshuawilson/merrit,thesamet/gerrit,bootstraponline-archive/gerrit-mirror,gcoders/gerrit,anminhsu/gerrit,quyixia/gerrit,thesamet/gerrit,gcoders/gerrit,MerritCR/merrit,hdost/gerrit,WANdisco/gerrit,gerrit-review/gerrit,TonyChai24/test,anminhsu/gerrit,joshuawilson/merrit,qtproject/qtqa-gerrit,quyixia/gerrit,qtproject/qtqa-gerrit,Overruler/gerrit,pkdevbox/gerrit,thinkernel/gerrit,Overruler/gerrit,gerrit-review/gerrit,Team-OctOS/host_gerrit,supriyantomaftuh/gerrit,qtproject/qtqa-gerrit,quyixia/gerrit,midnightradio/gerrit,Seinlin/gerrit,TonyChai24/test,anminhsu/gerrit,gcoders/gerrit,TonyChai24/test,midnightradio/gerrit,bootstraponline-archive/gerrit-mirror,hdost/gerrit,Overruler/gerrit,Seinlin/gerrit,jackminicloud/test,dwhipstock/gerrit,Team-OctOS/host_gerrit,Overruler/gerrit,Distrotech/gerrit,Distrotech/gerrit,thesamet/gerrit,Distrotech/gerrit,anminhsu/gerrit,thesamet/gerrit,bootstraponline-archive/gerrit-mirror,WANdisco/gerrit,netroby/gerrit,Saulis/gerrit,renchaorevee/gerrit,bootstraponline-archive/gerrit-mirror,pkdevbox/gerrit,GerritCodeReview/gerrit,dwhipstock/gerrit,Seinlin/gerrit,Overruler/gerrit,renchaorevee/gerrit,supriyantomaftuh/gerrit,GerritCodeReview/gerrit,thinkernel/gerrit,bpollack/gerrit,TonyChai24/test,WANdisco/gerrit,joshuawilson/merrit,qtproject/qtqa-gerrit,Saulis/gerrit,Overruler/gerrit,thinkernel/gerrit,netroby/gerrit,bpollack/gerrit,qtproject/qtqa-gerrit,renchaorevee/gerrit,renchaorevee/gerrit