Custom Graphics Tools

[NQNStudios]

I think this is pretty nifty.

• You can specify an image editor in the preferences, then launch it from the custom graphics window editing the current sheet.
• There is a reload button for capturing your external changes back into the interface/storing an undo action for those edits. (This isn't yet handled perfectly for sheets not contiguous with #0).
• Select a range of tiles in the current sheet for modification (still need to show them highlighted).
• Import other graphic icons on top of them
• Specify what graphic is the background, and the editor will do its best to strip it out for you
• Specify a new background, and the editor will overlay it for you.

(In other words, a possible solution for #554 )

This video shows me transposing cave walls onto grass:
https://youtu.be/qvR4MGFmUMI

[NQNStudios]

✅ The whole dialog should be managed by a class to get all the lambdas out of the giant function.

[NQNStudios]

Notes to self:

- frame custom dialog pic halves
- frame custom talk pic halves
- import monster graphic
- import tall monster graphic
- import wide monster graphic 
- import big monster graphic
- icon tool buttons re-frame the selection to icons that will be changed
	- bools for tall selection shape?
- all importing/framing classify?