Chunk free space detection/reporting

[ughman]

Chunks in the UI should show the amount of free space available within them, as well as indicate when they have been over-allocated. Entries should also indicate their size to give some idea of how the user might reorganize to fix packing errors.

[ughman]

I'll be making a new form used to rearrange entries. This form will also do the chunk packing checks, and will be what appears if you try to save while there's a packing error.