Add caused damage info to delta & make rgkit callable as a library

Hi everyone,

I am currently working on a self improving bot. It is important for me to get information about the outcome of the action of each robot. 
I also want the control over rgkit from my robot class (only in the training phase). Tell rgkit to play against these robots and so on.
The Runner class has a similar interface as the command line (`Runner.options` are basically the command line arguements).
To get information how your robots has done in the last round, I added damage_caused to the delta in GameState. You can register for the delta callback with `Runner(..., delta_callback=your_funciton)`.  This could be useful for other tools too (e.g. analyzing).