[btr] fix for the DEBUG-COSTMAP predicate:

it used to cause a recursive mutex lock
Merge branch 'master' of github.com:gaya-/cram_physics
Merge branch 'master' of github.com:gaya-/cram_physics
Merge branch 'master' of github.com:gaya-/cram_physics
Added .gitignore for robot_mask to ignore autogenerated python code (messages)
Added pancake as object instance for bullet worlds
Added symbols for pancake and pancakemaker
Merge branch 'master' of github.com:cram-code/cram_physics
Merge branch 'master' of github.com:gaya-/cram_physics
Merge branch 'master' of github.com:cram-code/cram_physics
Merge pull request #13 from fairlight1337/master

Just a few details; exporting symbols, adding an object-adder, updating .gitignore