Fixed cloneArtifacts task

All subprojects will be configured with an external repository.
Enforce USE_EXTERNAL_REPO setting before task execution

Change-Id: I606bbe7a8e3f15a433f2adb2e49097621520672d
Added tasks to create a maven style repo directory and zip file.

This will be delivered as part of the Android Studio installation
so users can use it without having to download additional bits.

Change-Id: I4c4afa07c669a0cdc46562b7bfa7e519d4d96968
Update version for base and gradle.

Change-Id: Ic4a966a264dc07b7f6d9571467c1a1180190e161