Less verbosity
Infrastructure for selectionXML2TClass attributes transfer

Infrastructure to have in TClass the properties specified in the
selection XML in place.
Workflow:
 o Add to the AST the class properties as AnnotatedAttr
 o Loop on class members and vars and add properties as AnnotatedAttr. Convention chosen:
   o transient : "//!" (good old tradition)
   o general : "PROPERTYNAME@@@PROPERTYVALUE"
 o Generate the code in the dictionary to read back these properties from the AST and modify TClass accordingly

The AST was chosen as the medium to carry properties to the dictionary generation because when PCMs are there, the information will be read back at library initialisation. Right now, since we deal with headers, the dictionaries carry the information.
The infrastructure allows to do all kind of manipulations concerning TClass according to the properties.
With this commit, only the "transiency" of members has been addressed.
Reasonable default verbosity after development burst