Definition
The version used by all android builds is now centralised in one location (so you don't have to upgrade the text in a hundred build.gradle files everytime we need the android gradle plugin to upgrade.
e.g.
dependencies {
classpath 'com.android.tools.build:gradle:0.11.+'
}
Upgrading
Send a pull request against RosAndroid.groovy on the appropriate release branch.
This pull request should modify the variable shown above. You'll usually be doing this in tandem with an android build tools upgrade. Damon has done this previously via a pull request that illustrates exactly what needs to be touched.
Also:
Update the version on the android studio download page on the wiki defining requirements.
Overriding
I haven't implemented an override, but this is probably feasible simply by checking if a variable has been set in the plugin. If you'd like this functionality, send us a pull request.