CrashEdit needs a better system for handling and solving packing errors

[ughman]

The error messages for packing errors are unhelpful, notably:

• _Which_ chunk the error occurred in is not reported at all.
• How much excess space is used is not reported either.
• If there is more than one packing error, only the first is reported.
• The error message does not describe what a packing error is.

The entire system should be redesigned. Preferrably, it should show entry sizes and remaining chunk-space live as the entries are modified. One possible design is this:

• Controllers gain the ability to invalidate themselves and their parents.
• Invalidated controllers have their names recalculated, and EntryChunkControllers recalculate their size minus capacity.
• Entries should have an EstimateSize method which returns their size in bytes. This method should be efficient so it can run every time a minor change is made to an entry's editor control. By default, it could return Save().Length as a slow default.

This setup would also have the side-benefit of having entity names updated in the tree view as their names are modified in the control.

[ughman]

Closing this issue, this is now part of issue #7