All contributions to this charm where made under Canonical
copyright; switch to Apache-2.0 license as agreed so we
can move forward with official project status.
Change-Id: I97206ee8be76220cb0937a09be3230432e04535a
Add charmhelpers.contrib.hardening and calls to install,
config-changed, upgrade-charm and update-status hooks.
Also add new config option to allow one or more hardening
modules to be applied at runtime.
Change-Id: If0d1e10b58ed506e0aca659f30120b8d5c96c04f