use new syntax for retrieving restore action list
only subscribe to action hooks and initialize monitoring when packrat mode is on at startup
log error initializing packrat monitoring
register for packrat actions and file monitoring in deferred init
Merge remote-tracking branch 'origin/master' into feature/pending-actions

Conflicts:
	src/cpp/session/modules/SessionPackrat.R
	src/cpp/session/modules/SessionPackrat.cpp