Merge pull request #11 from Jailander/master

Adding Topological Map field to recorded statistics
Added loading of map from file based on map_server code.
Added saving to db.
Added server node.
Added switching service with return for success/fail. Tested and working on two maps in rviz.
Adding basic usage docs.
More docs
Merge pull request #12 from hawesie/master

MongoDB-backed map switching node