Indicate when symbols are in the wrong order

[LagoLunatic]

Adds up/down arrows to the symbol list that indicate when a matching symbol is in the wrong order, as the order affects the bytes in the final binary but is otherwise difficult to notice.

Details:

• SymbolDiff.order contains the ordering of the symbol compared to its paired counterpart, or None for unpaired symbols.
• A symbol is only considered to be out of order if it's at the wrong spot in the list and it's wrong relative to the symbol that came before it, to reduce noise from excessive diffs.
• There is a "Wrong order" button at the top of the list that cycles the cursor through all of the wrong symbols when clicked. This is useful for very large objects with thousands of symbols in total, as scrolling through that many symbols manually and hoping to notice the wrong ones by eye can be time-consuming.

Closes #370