Core of XDNA diff mechanism
* Removing debug code from XDNA class
* Remove unnecessary json import
* single quotes -> double quotes for function descriptions
* Function description for XDNA::signatures_diff()
First version of new file format

Some last-minute amendements were made to the file format layout and naming, but this is all probably temporary anyway.
The new data it "saves" (the framerate) goes unused right now.
Save and load framerate from files.

Observe file opening to update framerate in UI.

This commit fixes #1.
Merge branch 'xdna-fileformat'

Conflicts:
	gui/animationwindow.py