This adds support for adding "personal" queues underneath any top-level
queue with automatic criteria inheritance.

Attempt to only use parentheses in WHERE clauses and friends when
mixing ANDed and ORed constraints

This retires the "Show assigned tickets on open queue" and "Show answered
tickets on open queue" settings.

And also fixup custom data fields used in conditions

The filter concept will allow for more sophisticated concepts including date
formatting, and will also allow plugin interaction.

And add options for custom data form fields