DOC: Promote developer-docs header to chapter and TOC [docs only]
DOC: Promote developer-docs header to chapter and TOC [docs only]

lpsinger/astropy,pllim/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,MSeifert04/astropy,pllim/astropy,astropy/astropy,lpsinger/astropy,saimn/astropy,StuartLittlefair/astropy,mhvk/astropy,bsipocz/astropy,MSeifert04/astropy,StuartLittlefair/astropy,pllim/astropy,dhomeier/astropy,larrybradley/astropy,MSeifert04/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,lpsinger/astropy,mhvk/astropy,dhomeier/astropy,bsipocz/astropy,aleksandr-bakanov/astropy,astropy/astropy,saimn/astropy,larrybradley/astropy,bsipocz/astropy,larrybradley/astropy,astropy/astropy,bsipocz/astropy,stargaser/astropy,saimn/astropy,saimn/astropy,lpsinger/astropy,stargaser/astropy,dhomeier/astropy,pllim/astropy,mhvk/astropy,pllim/astropy,astropy/astropy,lpsinger/astropy,saimn/astropy,mhvk/astropy,stargaser/astropy,MSeifert04/astropy,StuartLittlefair/astropy,larrybradley/astropy,stargaser/astropy,mhvk/astropy,astropy/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,dhomeier/astropy