COMP: Fix loading of external "loadable module" providing python script

Thanks to "Wang, Kevin" <kevin.wang@rmp.uhn.on.ca> for his help
identifying and testing the changes.

Co-authored-by: Wang, Kevin" <kevin.wang@rmp.uhn.on.ca>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22812 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Protect FilterWatcher from Progress before Start events

If the ShowProgress method is executed as an observer before
StartFilter method the ITK time probe will be stopped before the it's
started. This causes an exception. This case is just caught and ignored.

From: Bradley Lowekamp <blowekamp@mail.nih.gov>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22813 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Add escape sequence to quotes in CMake string

From: Bradley Lowekamp <blowekamp@mail.nih.gov>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22814 3bd1e089-480b-0410-8dfb-8563597acbee