STYLE: Make Python license headers be consistent in Python scripts
DOC: Add license header to commit msg hook script
STYLE: Miscellaneous fixes to import statements in commit msg hook
COMP: Use value initialization to zero-initialize thread id variable
COMP: Prefer splitting comma-separated pre-increment statements
COMP: Include `itkNumericTraitsCovariantVectorPixel.h` file in test
DOC: Fix Doxygen group name in math morphology class documentation
DOC: Use Doxygen citation command instead of misplaced `\par`