Support glossary attachments when creating entries

Important Note: when adding the entries, add some attachments On a glossary with categories. Open a glossary and add a new entry. Add another entry in offline or server down. Check that you don't see a sync button in offline. Go back online or turn server up and click synchronize. Check that entries have been stored. Finally, add another entry in offline with categories. Click on the offline entry. Check the categories you've previously selected are still selected. Edit files attached and save. Click again and check it has been edited. Go back online and wait for sync to trigger (could take more than 10 minutes). Check that entries are automatically sent and data is ok. Note: While MDL-57737 is not repaired, HTML will be squashed.