[[ ExternalsApiV5 ]] Added 'EngineApi' interface which the Android Engine class implements, together with accessor to externals API.
[[ ExternalsApiV5 ]] Added 'ActivityRun' method to Externals API (java-side).
[[ ExternalsApiV5 ]] Implemented RunOnSystemThread method in java LC class.
[[ ExternalsApiV5 ]] Implemented Wait object in java LC class.
[[ ExternalsApiV5 ]] Added simple test functions for activities and running on system thread.