BUG: Set the color range when changing number of colors

When copying a color table node and reducing the number
of colors in it, the color table range wasn't updated.
This led to problems in the Editor module when the selected
drawing integer wasn't matched up to the expected color.
Now when the number of colors is set on a user editable
color node, the range is set on the color look up table
and on the GUI slider at the same time.
Also updated the number of colors spin box to only trigger
a reset of the number of colors on the node on the editingFinished signal
as othewise cutting down a table from 300 to 50 colors could
empty out the table and refill it with black rather than 
creating a subset of the original table.

Issue #3115



git-svn-id: http://svn.slicer.org/Slicer4/trunk@21993 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix unused CMake variable Teem_VTK_TOOLKITS_IPATH warning

Following r21963, Teem_VTK_MANGLES is set to OFF. For that reason,
the variable Teem_VTK_TOOLKITS_IPATH is not required anymore.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21994 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Remove unused Slicer superbuild boolean variable

The variable "Slicer_BUILD_Extensions" originally introduced
by commit r21550 is not used.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21995 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix CMake warning related to WITH_MEMCHECK CMake variable

Commented the variable waiting the build system is updated to support
running of the test using valgrind.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21996 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix unused CMake variable warning related to DOCUMENTATION_* variable

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21997 3bd1e089-480b-0410-8dfb-8563597acbee