document jar sources and add javadoc

This .properties file is supported by the Android tools as a means to point
towards the javadoc for a given jar.  I've extended it to include a pointer
to the original download link and the source repo.
make-release-build: better submodule handling and faketime for ant build

Adding faketime to `ant release` means that the build will always start at
the same faked time on any machine.  This helps make the builds more
deterministic since the build will always start at the exact same time.
That time is the time of the most recent commit.
jenkins-build: use more robust submodule syncing
Merge pull request #69 from eighthave/courier

release build fixes, document jar sources and add javadoc