Issue #589: Add test-case to ensure empty hook-files are useless.
Issue #589: Add a self-test to the test-case.
Issue #589: Add a development utility for finding empty hooks.
Make find-empty-hooks print relative pathes.
Add decription of proposed usage to find-empty-hooks.
Issue #589: Remove empty hook files.
Close #589: Merge branch 'issue-589' into develop