run JUnit tests using android-junit-report to get XML output

Jenkins needs some kind of report from the JUnit tests in order to tell
whether the tests succeeded or not.  android-junit-report is a library to do
exactly that.  With this setup, Jenkins should now successfully understand the
status of the JUnit tests, where before it just ran them and ignored the
results.
add `ant javadoc` to generate javadoc for FDroid sources
script to do android ant configuration