Store log entries in a SQLite database

Summary:
As we open a connection at service start, and the broker
will submit one per one entries, we can use a SQLite database.

Test Plan:
Tests are provided to open, destroy a datastore, insert an entry.

They create and delete correctly the SQLite database file.

When we run insert_adds_a_row test, without a call to store.destroy():

$ sqlite3 log.db
SQLite version 3.15.1 2016-11-04 12:08:49
Enter ".help" for usage hints.
sqlite> .tables
log
sqlite> SELECT * FROM log;
2016-03-30T13:03:00Z|Sandlayth|#nasqueron-ops|Dwellers|docker start wolfphab

Reviewers: dereckson

Differential Revision: https://devcentral.nasqueron.org/D704