Split functionality of setting delete_moves_to_trash

Before it would handle two scenarios:
1) When a file is deleted
2) When a file has been modified

Scenario 2 now has it's own configuration called modified_moves_to_trash

DEBIAN/Makefile was trying to remove a file called greyhole-mv which does not exist causing the script to fail, have commented out until gboudreau adds that script into the repo.
New config option to allow the user to choose if old versions of modified files should be moved to the trash or not. Default to ON. Thanks to NovaKing.
greyhole-mv was never committed (and might never be); so let's not error out, if trying to build a .deb on a freshly cloned codebase