Rework FakeLogger to be more usable.
Remove pointless meddling with logging level
Take cpp-common with new test loggers
Prevent memory leaks in the AnalyticsLogger
Remove unnecessary take_over() calls
Update cpp-common
Merge branch 'dev' into fakelogger

Conflicts:
	sprout/ut/hssconnection_test.cpp
Take latest cpp-common fakelogger
Remove fakelogger.hpp from tests that don't need it
Clean up AnalyticsLogger based on code review feedback
Take latest cpp-common and update #includes
Merge remote-tracking branch 'origin/dev' into fakelogger
Merge pull request #616 from Metaswitch/fakelogger

[Reviewer: Andy] Rework the fake logger used in UTs