Scala Library as a test + improvment of benchmark

- Addition fo the Scala library (2.12) as compilation test
- Improvement of the benchmark for global ratio
- Source selectivity in build.scala to build only specific file.

TODO:
- Improve the benchmark for counting number of failed test and successful ones
- Abstract the source selectivity under a command
- All the rest...
Merge branch 'master' of https://github.com/aghosn/persistence