BUG: Fix crash when using slicer dark style

When painting a tab, Cleanlooks style expects to have a gradient in the
Window palette brush when it finds a gradient in the Button palette
brush.
Issue #3251

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22283 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Fixed excessive memory consumption in the undo/redo buffer of the Editor module (http://www.na-mic.org/Bug/view.php?id=3283)

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22284 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: fix warnings about signed/unsigned mismatches

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22285 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: 3228. Added preset parameters to TractographyInteractiveSeeding module for compatibility with Slicer3 Fiducial Seeding and Slicer3 Labelmap Seeding. 

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22286 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: fix compile warnings, unused variables, (un)signed, trailing spaces

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22287 3bd1e089-480b-0410-8dfb-8563597acbee