Add topic name functionality

I added two functions to the Matlab Bag class:
* topics returns a list of topics in a bag and the message type of each topic and takes an optional input regular expression to match topic names.
* topicType returns the message types that are being published on the input topics.

I updated the definition method so that now it accepts as input either a message type or a topic name.
I updated the instructions in COMPILING.md to use rosinstall_generator.