Added sqlite3 sessions and tests. Fixes to compilerunloop.

Added flag to know when server is listening, to properly stop listening.
Sessions are now a class, with sessions_mem is old mem style sessions, and
new sessions_sqlite3 a sqlite implementation, using json as session data.
Different scenarios may need new session backends.
Added dict read from json, but only onion dict subset.
Merge branch 'master' of github.com:davidmoreno/onion