Refactor map events

Most of the map event attributes have been moved to event components as they are optional.
This PR also introduces more warnings to be printed.

Probable Incompatibilities to current game data sets:
Events, which intend to trigger the stash, should just have type=stash and do not need to have the stash=true attribute any more. So if there are events by now, which do not have the type=stash, but do have the stash=true attribute, these events will break.
There are no occurrences in flare-game nor in polymorphable.