Force target selection on filter form
Add minor code improvements

* Change table name from ost_email_filter* to ost_filter*
* Add patch for target field.

* Collapse date settings into system settings.
* Move auto-cron setting to emails settings page.
* Move clickable urls setting to tickets settings page.

This will help distinguish between the knowledgebase part which encompasses
FAQ's and canned responses, and the FAQ part which contains the articles
detailing frequently-asked-questions.

And remove unsupported filter of email headers

But don't send out canned responses for new tickets that matched a filter
with an attached canned response if that response is not enabled. Also,
explicitly block deletes to filters that are in use.

- Move access to it's own table.
- Refactor what department membership means in relation to group access

when they are in use by email filters

Add print options supports - staff can now print a ticket thread without internal notes + select paper size on the fly