ENH: Added table node export to LabelStatistics module

Changed exporting to file to exporting to table. It does not require any additional input from the user, user can copy-paste data or save table to file.
Also fixed LabelStatistics save function (when labelmap volume had to be resampled then the resampled volume did not have display node and that caused the saving to fail). It is not only available through Python, not from GUI.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24787 3bd1e089-480b-0410-8dfb-8563597acbee