Optimizing imports
 * removing unused ones
 * eliminating wildcards
 * ensuring alphabetical order
fixing license mix issue - we're using Apache one
moving Version class to _private package
resuscitating UNREQUIRED flag
Using bit flags instead of DependencyFlag array
Add a problem report when dependency cycle is detected.
Add Service log messages to service lifecycle whenever appliable.
Add a basic test for parent dependencies and fix bugs found in ParentDependency
CheckDependencyCycleTask.checkDependencyCyle must use ServiceContext to create tasks, and not the Transaction
At ProblemReport.addProblem, update maxSeverityLevel if new severity is larger than current maxSeverity value
WIP (tests broken, do not pull): Revert transaction if report is not committable.
Also, invoke commit listener when transaction is rolling back (under review).