Libgdx 1.2.0 Update

This branch contains an update of the libgdx library to Version 1.2.0.
As from now it will be possible to change the libgdx Version by changing the gdxVersion value in the project's build.gradle file.
could you put these tasks into an own file and link it like "apply from: 'gradle/adb_tasks.gradle'" at the top?