Moved action handler related code into a separate file

Since the action handlers are getting quite numerous and make the process-module.lisp file seem a bit cluttered, they are moved to a designated file.
Replaced `pr2-manip-pm' by the full name `pr2-manipulation-process-module'

The nickname inside the .asd file is left there for compatibility reasons for now.
Added the `missing' predicate to list objects missing in a list
Added the `flatten' predicate
Added predicate to find available arms w.r.t. objects in hand
Added new, cleaner predicates for grasp decisions
Removed the `*handle-...' prefix from grasp- and pregrasp poses

The given poses are valid for all kinds of objects, not just handles.
Removed obsolete predicates
Added predicates for optimal grasp calc and grasp assignment class
Added predicate for finding the absolute pose of a handle on an object
Largely refactored handled-objects.lisp to be more meaningful, less cluttered
Fixed predicates for minimum handles to use and hands in use
Fixed computation on optimal arm/pose/handle assignments when grasping
Refactored the handler for grasping such that it grasps objs w and w/o handles
Actually commited the new grasping action handler
Generating a pose that is pointing away from the robot before grasping objects
Added an `ignore' for a parameter not in use
Refactored `execute-grasp'
Corrected relative pose generation for grasping
Fixed coordinate frame transformations for grasping (which now works again)