Refactor default package and common package (Breaking change) #92
Description
Currently, we almost always have some classes in copper.coreengine.core default package and some in copper.coreengine.core.common. The choice which packages resides in where seems to be almost arbitrarily and makes no sense.
We should refactor this appropriately (As these are many classes, we might introduce some other packages with a more meaningful classification).
As there are interfaces in both packages, this refactoring will introduce breaking changes to our users who will in turn need to update package pathes. So we should apply this change only for a new major version release.
Along with that refactoring, the TicketPoolManager and DefaultTicketPoolManager should be moved from the default package to tranzient as its usage is really bound to transient engines and makes no sense for a persistent engine. (Ticket pool managers can't be set and used in their anyways).