Squashed UserBricks Commits

Since it's the GSoC "soft deadline" today I decided to start this pull request. 

If you don't already know, this was my GSoC project: to implement custom bricks in Catroid, similar to user-defined functions in a programming language.

There are some documentation files about the project collected in a google drive folder here: https://drive.google.com/folderview?id=0B1qnfN89gHX7eWRobmREbHhiMVE&usp=sharing

Also, if you are on JIRA, this is my agile board: https://jira.catrob.at/secure/RapidBoard.jspa?rapidView=17

I achieved my goals, but I was unable to go beyond them and implement some extra goodies that I'd planned in case I had extra time.

This branch is not necessarily ready to merge into master: I still have some work to do.

Problems with the main program:
   • Bug in my placholder graphics.
   • Needs ability to delete user bricks.
   • I'm not getting checkstyle errors, but I know some things might not be up to the coding standards.

Problems with the tests:
   • Some of the user bricks tests and pretty sparse, some more things could be tested.