Added JSON output and Boogie printing

Added -json option to produce report in json format and -b filename option to print the internal boogie program. Note that our Boogie output may not be compatible with the latest version of boogie.

As in the previous version, run with:

cd your-project
python /path/to/bixe/runner.py -- gradle clean compileJava [or ant, or mvn, depending on your build system]
// Note that you have to do a clean build, otherwise bixie will only analyze the delta.
cd bixie_report1
open index.html