Rethink policy integration in actions

Powerdevil actions have an integrated system to check for certain "policies". Policies here means "Don't turn off/lock the screen" or "Don't suspend" e.g. while a media player is playing.

An action sets required policies and trigger() checks for those (unless the "Explicit" parameter is passed to trigger()).

While a nice idea on the surface I think it gets more in the way than helping. More often then not we pass "Explicit" to override this anyway, and we have a bit of a mess with calling trigger() and/or triggerImpl(). Using QVariantMap to pass data to trigger() also isn't nice API.

I think we would be better off without this system and explicity check for inhibitions in the few places where we need it