Nailgun object interface for ActionLog added

Single and collection objects for ActionLog entity added to nailgun
objects system. It needed for further utilization by logic which sends
this data to collector service.

JSONSchema for aforementioned entity defined.

Unit tests updated.

Change-Id: Icf40bdb84785f64e9e43025d69482451c8de6ea4
Implements: blueprint send-anon-usage