[BREAKING CHANGE] Move modules to src and tests and i18n, UnicodeJS to lib

Move UnicodeJS into lib/ as it's now a library. Take advantage of this to move
modules/ve to src/ except for tests, which move to tests/, and messages, which move
to i18n/, moving the repo to be much closer to how others are structured.

Change-Id: Ic0f0354da9e1c38ec3ac349120ec9e3348b14556