PerfCounters: implement basic infrastructure for instance tracking
BaseZetboxDataContext: remove GC manipulation
PerfMon: implement ZetboxContext monitoring
Autofac: use the OnActivating to initialize instances

OnActivat*ed* is only called AFTER the instance is deemed constructed
by Autofac. Therefore it is possible to receive an instance before it
is finished. Using OnActivat*ing* instead keeps the instance locked until
the initializer is run.
PerfCounter: improve formatting, increment Total when instance is created
PerfCounter: protect decrement from double dispose
PerfCounterDispatcher: fix filenames
PerfCounter: Apply LifetimeScope lifetime tracking behaviour
IdentityResolver: Implement caching and singletonization