go.tools/godoc/blog: add PlayEnabled and GodocURL options
go.tools/godoc/blog: add PlayEnabled and GodocURL options

Also make NewServer take a Config, not *Config.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/13755044

golang/tools,runcom/tools,cw2018/tools,cmars/tools,argandas/tools,magiccao/tools,matryer/tools,cmars/tools,syreclabs/go-tools,maddyonline/tools,springning/tools,maddyonline/tools,maddyonline/tools,argandas/tools,josharian/tools,cw2018/tools,syreclabs/go-tools,cmars/tools,glasser/golang-tools,syreclabs/go-tools,josharian/tools,golang/tools,glasser/golang-tools,maddyonline/tools,josharian/tools,golang/tools,runcom/tools,magiccao/tools,dmitris/tools,golang/tools,matryer/tools,magiccao/tools,cw2018/tools,cw2018/tools,sshetty10/tools,jdhenke/tools,sshetty10/tools,syreclabs/go-tools,sshetty10/tools,4ad/tools,syreclabs/go-tools,dmitris/tools,jdhenke/tools,matryer/tools,cmars/tools,4ad/tools,magiccao/tools,springning/tools,runcom/tools,nicot/tools,nicot/tools,josharian/tools,glasser/golang-tools,jdhenke/tools,matryer/tools,argandas/tools,runcom/tools,nicot/tools,sshetty10/tools,dmitris/tools,dmitris/tools,springning/tools,4ad/tools,argandas/tools,springning/tools,nicot/tools,jdhenke/tools,golang/tools,glasser/golang-tools,syreclabs/go-tools