Rewrite the logger to have pluggable output and more verbosity levels.
Rewrite the logger to have pluggable output and more verbosity levels.

Non informational messages are now logged to stderr instead of stdout.

chalucha/vibe.d,veelo/vibe.d,alphaKAI/vibe.d,sigod/vibe.d,dkillebrew/vibe.d,alphaKAI/vibe.d,nathanchristenson/vibe.d,nathanchristenson/vibe.d,rejectedsoftware/vibe.d,schuetzm/vibe.d,Geod24/vibe.d,fast4shoot/vibe.d,jkm/vibe.d,Yoplitein/vibe.d,jkm/vibe.d,AndreyMZ/vibe.d,1100110/vibe.d,ColdenCullen/vibe.d,Yoplitein/vibe.d,etcimon/vibe.d,Mihail-K/vibe.d,Yoplitein/vibe.d,alphaKAI/vibe.d,etcimon/vibe.d,etcimon/vibe.0,mfrischknecht/vibe.d,DBankov/vibe.d,nathanchristenson/vibe.d,redstar/vibe.d,machindertechnologies/vibe.d,etcimon/vibe.0,sigod/vibe.d,sigod/vibe.d,Kozzi11/vibe.d,yannick/vibe.d,gedaiu/vibe.d