gtk gui frontend

[Aeva]

Nothing fancy, probably using tkinter for portability reasons went with gtk.

Some remaining things to do:

• [x] hook up the converter scripts
• [x] progress visualizer window
• [x] update progress window while converting levels
• [x] "progress completed" popup
• [x] run converters in a thread pool
• [x] license text in about page
• [x] order of path chooser buttons should be changed, so that tileset happens after sprites dir.
• [x] when the sprites dir is picked, I think that means the "current_folder" for the tileset could be set, making it a little easier to find your tileset.
• [x] clear the level list when finished
• [x] freeze main window while converting levels
• [x] don't render paths redundantly / consolidate redundant level paths
• [x] generate the tileset xml file #14
• [x] file paths in export should be relative, not absolute (to where?) #14
• [x] program icon
• [ ] relative paths in tree view
• [ ] multi-nesting of directories in tree view
• [ ] tree view icons (folder vs level)
• [ ] the add level dialogue's working dir should either be the directory of the last level added, or the executable's working dir
• [ ] drag-and-drop

[Aeva]

For reference with the tree view stuff:

• http://python-gtk-3-tutorial.readthedocs.io/en/latest/treeview.html
• https://developer.gnome.org/gnome-devel-demos/stable/treeview_cellrenderertoggle.py.html.en
• http://arstechnica.com/information-technology/2009/08/howto-an-introduction-to-gtk-treeviews-and-autocompletion/

[Aeva]

I'm going to consider this closed now, since all of the essential features are here now, and will move the refinements into other tickets.