In TFormula and TTreeFormula add support for the ternary condition operator ( c ? i : e )

In TSplot, TSpider, TSelectorDraw, TTreePlayer, TTreeTableInterface update the parsing
of colon separated line to properly handle the ternary condition operator, reduce 
code duplication and fix existing parsing bugs (due to the 'almost' duplicated code
syndrome):
  - Removed TSelectorDraw::MakeIndex and TSelectorDraw::GetNameByIndex
  - Added TSelectorDraw::SplitNames to replace those 2 function plus pre-processing code
      that was always used in conjunction with their calls.
  - Updated the calling points to use TSelectorDraw::SplitNames.
  - Removed the unused (and incorrect) TTree::MakeIndex and TTree::GetNameByIndex.


git-svn-id: http://root.cern.ch/svn/root/trunk@30157 27541ba8-7e3a-0410-8455-c3a389f83636