Jumps to the first offset associated with the change at the top of
the Undo stack. We generally jump to the code/data offset, not the
specific line affected. It's possible to do better (and we do, for
Notes), but probably not worthwhile.
This involved adding a list to the DisasmProject, creating a new
UndoableChange type, and writing the project file serialization
code. While doing the latter I realized that the new Width field
was redundant with the FormatDescriptor Length field, and removed it.
I added a placeholder line type, but we're not yet showing the
table in the display list. (To edit the tables you just have to
know where they are.)
