equipt TCanvas custom streamer to provide data members information for TBufferJSON/TBufferXML/TBufferSQL2 classes
Fix problem with streamer infos reading from TXMLFile
fix problem with equipt custom streamers, add missing comment

Conflicts:
	io/sql/src/TBufferSQL2.cxx
Update in TBufferJSON (bug fix and follow up on change in core and io)

1. Fix problem with equipt custom streamers
2. Implement TBufferJSON::CheckObject(), enable correct storage of colors palete in JSON with TCanvas
3. Remove test object
remove debug output from TCanvas::Streamer