First version of new MainEntry.

Copied the class MainEntry to ab.agent package, so there should be no compatibility issues. The new MainEntry class should be easier to expand.
NaiveAgent now also extends the Agent class to simplify the agent instantiation.
The new MainEntry class supports an interactive mode (-i).
Removed run method from NaiveAgent
Changed option syntax for level selection.

Now there has to be a -lvl flag before the level number. So for example, instead of "-ua 1 -showSeg", it should be "-ua -lvl 1 -showSeg".
Merge pull request #4 from crisHH/tsschaffert/startupChanges

First version of new MainEntry.