Better handling of drops on a tabular editor.
Merge branch 'master' into fix/qt-tabular-drag
Fixes for DnD on Qt4 TabularEditors.

This should bring to rough feature-parity with Wx TabularEditor DnD.
Add better DnD support for Qt4 TableEditors.

This probably needs more thorough testing.
Add support for images to Qt4 TableEditor.
Fix flags for empty region.
Code clean-up.
Add a change log file for traitsui.
Merge pull request #135 from enthought/fix/qt-table-drag

Qt TableEditor and TabularEditor improvements