Refactor unit tests

The existing unit tests work, but the setup is really not amenable to
the addition of additional tests in a modular fashion. This splits
things out so there is a framework for tests in Lua, and all a module
has to do on the Lua side is supply a list of functions to call and
results to expect. And then on the php side, only one array entry and
two short functions need to be added to LuaSandboxEngineTest to run the
tests.

Change-Id: Ib241b246aa0c7223c33887b38a5858582d7d31b0
Merge "Refactor unit tests"