The port to using Gradle only.

Sorry for the huge slew of commits D:
Works, compiles.

f1355bf is the last commit still using ant as the main buildscript base. After that, I switched to gradle only.

It was a pain trying to rebase the latest 4 commits, and I ended up just copying them over.

Some caveats:
gradle cannot replace tokens in .java files -- @FINGERPRINT@ @BUILD_NUMBER@ and @VERSION@ are not replaced in EquivalentExchange3.java and Reference.java.
AbrarSyed solved this by using a separate properties file?
gradle does not like doing incrementing build numbers. -- We have to do it manually, or with an environment variable.