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
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