Added MoreApps methods (but Android crashing)

Hi, I added methods for the MoreApps functionality of Chartboost, but I can't get it working for Android. I get a crash at `startSession` with the trace `[Chartboost] Error - Extension Context is null.`. This does not happen with your binaries, but happens even if I simply recompile your last commit without any modifications, so it's not coming from my code modifications, but probably from the build process or something :(