Port over FORMS_EXTRA_WIDGETS feature from forms-builder.
Port over FORMS_EXTRA_WIDGETS feature from forms-builder.

readevalprint/mezzanine,Skytorn86/mezzanine,spookylukey/mezzanine,Kniyl/mezzanine,frankchin/mezzanine,tuxinhang1989/mezzanine,ZeroXn/mezzanine,emile2016/mezzanine,gradel/mezzanine,industrydive/mezzanine,adrian-the-git/mezzanine,dovydas/mezzanine,jjz/mezzanine,agepoly/mezzanine,saintbird/mezzanine,biomassives/mezzanine,dekomote/mezzanine-modeltranslation-backport,wbtuomela/mezzanine,batpad/mezzanine,sjdines/mezzanine,vladir/mezzanine,dustinrb/mezzanine,Kniyl/mezzanine,molokov/mezzanine,ryneeverett/mezzanine,Cajoline/mezzanine,Kniyl/mezzanine,nikolas/mezzanine,readevalprint/mezzanine,AlexHill/mezzanine,frankier/mezzanine,douglaskastle/mezzanine,wyzex/mezzanine,sjdines/mezzanine,theclanks/mezzanine,ZeroXn/mezzanine,biomassives/mezzanine,industrydive/mezzanine,theclanks/mezzanine,agepoly/mezzanine,emile2016/mezzanine,Cicero-Zhao/mezzanine,christianwgd/mezzanine,dustinrb/mezzanine,SoLoHiC/mezzanine,agepoly/mezzanine,stephenmcd/mezzanine,damnfine/mezzanine,gradel/mezzanine,adrian-the-git/mezzanine,nikolas/mezzanine,wbtuomela/mezzanine,sjdines/mezzanine,sjuxax/mezzanine,mush42/mezzanine,ZeroXn/mezzanine,ryneeverett/mezzanine,cccs-web/mezzanine,vladir/mezzanine,joshcartme/mezzanine,wyzex/mezzanine,christianwgd/mezzanine,molokov/mezzanine,Cajoline/mezzanine,dsanders11/mezzanine,damnfine/mezzanine,webounty/mezzanine,vladir/mezzanine,frankchin/mezzanine,dekomote/mezzanine-modeltranslation-backport,christianwgd/mezzanine,jerivas/mezzanine,jjz/mezzanine,dekomote/mezzanine-modeltranslation-backport,jerivas/mezzanine,fusionbox/mezzanine,viaregio/mezzanine,fusionbox/mezzanine,emile2016/mezzanine,promil23/mezzanine,theclanks/mezzanine,wbtuomela/mezzanine,wyzex/mezzanine,saintbird/mezzanine,dsanders11/mezzanine,dovydas/mezzanine,biomassives/mezzanine,eino-makitalo/mezzanine,douglaskastle/mezzanine,webounty/mezzanine,promil23/mezzanine,ryneeverett/mezzanine,mush42/mezzanine,frankier/mezzanine,gradel/mezzanine,frankchin/mezzanine,readevalprint/mezzanine,viaregio/mezzanine,cccs-web/mezzanine,joshcartme/mezzanine,tuxinhang1989/mezzanine,douglaskastle/mezzanine,eino-makitalo/mezzanine,mush42/mezzanine,viaregio/mezzanine,adrian-the-git/mezzanine,jerivas/mezzanine,SoLoHiC/mezzanine,frankier/mezzanine,nikolas/mezzanine,geodesign/mezzanine,industrydive/mezzanine,PegasusWang/mezzanine,Cicero-Zhao/mezzanine,Cajoline/mezzanine,molokov/mezzanine,joshcartme/mezzanine,batpad/mezzanine,PegasusWang/mezzanine,dsanders11/mezzanine,webounty/mezzanine,dustinrb/mezzanine,SoLoHiC/mezzanine,eino-makitalo/mezzanine,tuxinhang1989/mezzanine,jjz/mezzanine,Skytorn86/mezzanine,PegasusWang/mezzanine,geodesign/mezzanine,sjuxax/mezzanine,dovydas/mezzanine,damnfine/mezzanine,stephenmcd/mezzanine,geodesign/mezzanine,spookylukey/mezzanine,AlexHill/mezzanine,Skytorn86/mezzanine,promil23/mezzanine,spookylukey/mezzanine,saintbird/mezzanine,sjuxax/mezzanine,stephenmcd/mezzanine