fixed deprecation warning and python2 compatibility
added basic persistence

the state of the world can be stored in dict object and also restored from it
this dict object is meant to be converted to and stored in JSON format

also note: I deactivated the dictproxy stuff in world.py since it caused a segmentation fault
added methods to world for storing to and restoring from a JSON string
world now copies all of infoAllWorld that it modifies to prevent side effects
added folder for unit tests with a first test class for persistence
added .ropeproject folder to .gitignore