Introducing new types of action designators: Constraint designators

I'd like to have a new type of action designator, namely constraints designators. I want to clearly separate them from the "regular" trajectory designators in the PR2 manipulation process module. In order to check for these I added a new predicate constraints-desig?.

The changes I made are small. However, since it is cram_core I wanted someone else to explicitly look over my changes. Hence, the pull request. ;)