ENH: Add special column type in qMRMLTableView to display checkboxes for boolean values

If a vtkBitArray is added as a column to vtkMRMLTableNode, then qMRMLTableView shows a checkbox instead of 0/1 text to make it easier to edit.
In the future color, position, and other data will possibly be added as further types. The mentioned two will be the same value type (double array), so will need to specify not just type but display option too.
qMRMLTableItemDelegate that will deliver this functionality is removed form the repository (it was temporarily added in the previous commit so that it can be accessed and uesd later).
Commented out lines were removed from other classes. Having commented code in the repository makes no sense: the repository itself can be used as a history, no need for three year old comments to make the code harder to read.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24970 3bd1e089-480b-0410-8dfb-8563597acbee