Document `develop_git` command for switching from SVN repo to Git mirror
Document `develop_git` command for switching from SVN repo to Git mirror

Resolves 773

tpkemme/TVV,cristovaov/VVV,speartail/VVV,tomjn/varying-vagrant-vagrants,erikjoling/VVV,Haimanot1989/vvv-at-senitel,saucal/VVV,zaantar/vov,miya0001/VVV,killa-kyle/vvv,ericandrewlewis/VVV,ericmann/VVV,rooftopcms/VVV,erikjoling/VVV,salcode/VVV,ericandrewlewis/VVV,mattbanks/VVV,tim-steele/VVV,Varying-Vagrant-Vagrants/VVV,WybrenKoelmans/VVV,harvestweb/VVV,harvestweb/VVV,zaantar/vov,speartail/VVV,WybrenKoelmans/VVV,writecodedrinkcoffee/VVV,mikesprague/VVV,miya0001/VVV,TobiasBg/Varying-Vagrant-Vagrants,cristovaov/VVV,saucal/VVV,clreed87/VVV,mikesprague/VVV,mattbanks/VVV,tpkemme/TVV,mattbanks/VVV,Varying-Vagrant-Vagrants/VVV,salcode/VVV,tpkemme/TVV,ericmann/VVV,DrewAPicture/varying-vagrant-vagrants,tim-steele/VVV,tomjn/varying-vagrant-vagrants,TobiasBg/Varying-Vagrant-Vagrants,trepmal/varying-vagrant-vagrants,saucal/VVV,DrewAPicture/varying-vagrant-vagrants,rooftopcms/VVV,killa-kyle/vvv,writecodedrinkcoffee/VVV,Haimanot1989/vvv-at-senitel,cfoellmann/VVV,trepmal/varying-vagrant-vagrants,clreed87/VVV,Varying-Vagrant-Vagrants/VVV,cfoellmann/VVV,tpkemme/TVV