Fixed issue 29 - renaming tags does not mark diary as modified
Fixed issue 29 - renaming tags does not mark diary as modified

tk_main.py:
Renamed variables: .is_modified => .entry_modified
.options_modified => .diary_modified (to better reflect the usage of these variables)
Renamed functions: _SetModified => _SetEntryModified
_SetOptionsModified => _SetDiaryModified (to match the change in the variables)

tk_main.py
(_RenameTag()): Added call to _SetDiaryModified(True) so the user can be warned about saving changes to tags

Isendir/thotkeeper,cmpilato/thotkeeper