[cram_pr2_knowledge] implemented GRIPPER-LINK predicate for pr2
Merge branch 'master' of https://github.com/cram-code/cram_physics
[btr] working on the list of objects with disabled collisions in the world:

- renamed the predicate from ROBOT-NOT-IN-COLLISION to OBJECT-NOT-IN-COLLISION
- the list of disabled objects now contains lists with pairs of objects
- renamed the list of disabled objects into DISABLED-COLLISION-OBJECTS
[btr] ADD-OBJECT now accepts a key DISABLE-COLLISIONS-WITH,

which is a list of object names.
Added IK-SOLUTION-NOT-IN-COLLISION predicate for the robot:

it checks if the generated ik solution would cause the robot to collide
with its environment. When :grasping key is supplied, collisions
with robot's gripper links are discarded, as it is assumed that
the ik solution is for grasping an object and should cause collisions.
[btr] Got rid of ugly Prolog code for adding objects:

now the extra key (DISABLE-COLLISIONS-WITH) is handles by Lisp.
[btr-desig] ROBOT-NOT-IN-COLLISION -> OBJECT-NOT-IN-COLLISION.
[spatial rels] minor updates
[cram_env_repr]: defined dummy occasions for OBJECT-PICKED & ARMS-PARKED.
minor
[spatial_rels] Removed demo code from the package.
Removed VISIBILITY_COSTMAP. It's in CRAM_EXPERIMENTAL now
Removed TRIANGULATE_POINT_CLOUD, it's in CRAM_EXPERIMENTAL now.
Removed ROBOT_MASK, it's in CRAM_EXPERIMENTAL now.
Removed BULLET_REASONING_DEMO, it's in CRAM_DEMO now.
[btr] added a spatula model
spatula is a designator property now.
[btr] fix for the DEBUG-COSTMAP predicate:

it used to cause a recursive mutex lock
[btr] the spatula had a wrong orientation, fixed the model
[pr2_knowledge] the orientation should also mattter for spatulas