Delimited text reader not correctly stripping spaces

See paraview bug 13962 (http://paraview.org/Bug/view.php?id=13962). If
there are spaces after numbers, vtkVariant will not convert the number
properly. The fix is to make istringstream also take in the white space
after conversion so that it returns in proper state.

Change-Id: I9d488c5b14e840875f0716a667cbc29991837df6
Merge topic 'delimited_text_reader_bug' into master

0db52347 Delimited text reader not correctly stripping spaces