Multiple folders (aka tagging support)

Implement several command for folder management and message tagging.
Multiple folders (aka tagging support)

Implement fake classes for compiling with tagging commands.
Multiple folders (aka tagging support)

Implement fake classes for compiling with tagging commands.
Non-relational persistence

Improve the dependency injection mechanism. Now, all
manager classes (SystemFacade, FolderManager, ...)
present a variation point with respect to the dao factory.

This way, the PersistenceFeature aspect *injects* the proper
factory into these classes, whenever the method getDaoFactory()
executes.