Full Gradle Build and more

Hi Toby,

I've updated the examples and the build, such that they are now all build with gradle including the Xtend compiler. I also had to upgrade the SDK version 1o 11, because lint was complaining. Not sure if that is a problem and should be solved differently (i.e. ignore lint or remove the dependencies to SDK 11).

I also added the possibility to write @AndroidActivity(R.layout.main) instead of @AndroidActivity(layout=R.layout.main) which is still supported.

thanks,
Sven