added Json handling and @contentType UDA
Update common.d

fixed ddoc for ContentTypeAttribute
adhered to styleGuide
fixes compileation of diet-templates with GDC
Merge branch 'gdc-fixes' into patch-web.web
to enable compilation with gdc
added nice alias
HTTPRequestDelegats are now passwd through
and enable callbacks in web.web classes
so WebSocket functionality can be used
FIXUP pipe parameters through
removed unused import
Merge branch 'patch-web.web' of https://github.com/UplinkCoder/vibe.d