Tests the validity of all the operators against all the custom field clauses.
This is not intended to be an exhaustive test of each clause. It's primary goals are to:
- ensure that the operators that should work with a clause don't cause a validation error, and that some kind of
sensible result is returned
- if the operator does not validate, that an appropriate error is displayed
RAID-839: This test now has some (not all) escaped operators,
It is because some tests are run by http unit and some validated locally.
Change is done because new Tomcat won't accept some characters.