Fixes #343: Add configurable version check

The interface VersionCheck was introduced. Users can implement this
interface and register their own VersionChecks with
TabrisClientInstaller.setVersionCheck. The old version check was ported
to also implement VersionCheck. The TabrisClientInstaller uses teh old
version check as it's default.

Change-Id: I8e06b0bb0619b265b9fa2e964208c218a2da26fa