Restructure project for test apps

This CL updates project to use a local maven repo.
(local as in near source code w/ relative path).
This is necessary to have multiple versions of the
project on the same computer also provides better
separation.

I also moved integration tests to depend on these
because we cannot build the compiler and test app at
the same project.

I've changed library plugin's jar to be a separate
upload task to avoid some build issues in TestApp
when we release a @jar and @aar with same group and
artifact ids.

This CL also adds some convenience methods to
gradle build script to run all tests, prepare maven
repo, run integration tests etc. These were needed
to do CI.

Bug: 19718690
Change-Id: I3c80e09fe7c8c2780ca00c3e9b9ba99a162531cf