[!!!][FEATURE] FileMonitor now uses identifier and has getIdentifier()
This change makes the FileMonitor use the identifier internally and
provides a getIdentifier() method. With this, using multiple file
monitors becomes feasible.
The "ChangeDetectionStrategyInterface" contains the two new methods
"setFileMonitor" and "shutdownObject" now, so if you implemented your
own change detection strategy, you need to implement those.
The ModificationTimeStrategy provided with FLOW3 is no longer singleton
and thus usable with multiple file monitor instances in parallel.