First try: get Orbot "Internals" accounting

This part isn't easy: try to get Orbot bandwidth usage without having
the applications in it.

Orbot uses some MB in order to query Directories, it may be good to get
them in order to have some accurate accounting.
Problem: filtering such traffic isn't easy, as ports aren't fixed "for
good":
- some are dynamically allocated
- others may be moved in the confuguration file

Thus, this part will be hard.
This explains why the default Orbot "transparent proxy" doesn't show up
per-app bandwidth usage, but Orbot itself.