Allow fab_quiet to shush warnings/errors.
Allow fab_quiet to shush warnings/errors.

This should ideally be broken out into a more granular definition of "quiet",
such that one can say they want to quiet the "run:" note, and/or stdout, and/or
stderr, and/or warnings, and/or...etc. Instead of a blanket setting.

bspink/fabric,qinrong/fabric,likesxuqiang/fabric,elijah513/fabric,rodrigc/fabric,felix-d/fabric,jaraco/fabric,tekapo/fabric,bitprophet/fabric,bitmonk/fabric,MjAbuz/fabric,rbramwell/fabric,SamuelMarks/fabric,itoed/fabric,cmattoon/fabric,mathiasertl/fabric,raimon49/fabric,getsentry/fabric,ploxiln/fabric,akaariai/fabric,askulkarni2/fabric,amaniak/fabric,hrubi/fabric,kxxoling/fabric,pashinin/fabric,TarasRudnyk/fabric,simon-engledew/fabric,kmonsoor/fabric,fernandezcuesta/fabric,opavader/fabric,xLegoz/fabric,pgroudas/fabric,ericholscher/fabric,sdelements/fabric,cgvarela/fabric,StackStorm/fabric,rane-hs/fabric-py3,haridsv/fabric,tolbkni/fabric