Merge pull request #2 from montegoulding/feature/externals_v5

Feature/externals v5
[[ 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.
[[ ExternalsApiV5 ]] Initial changes to lcidl syntax to better support cross-platform externals.
Merge commit 'f509a647704fdcbc61f1cc17fa40786249eb0ba3' into feature/externals_v5