fix #498

Note:

The effect of this fix is that if a metadata field is disabled and an
image is refreshed, that field in the database will be insured to be
NULL.
Make sure the incoming rating isn't higher than what is allowed
Merge pull request #499 from SubJunk/master

Make sure the incoming rating isn't higher than what is allowed
fix typo
fix typo in tab link
implement formatting for printImageMetadata
Fix typo
Merge remote-tracking branch 'origin/master' into 1.4.6