Merge TileOven into TileMill

[Komzpa]

Can TileOven changes be in principle merged into upstream Tilemill repo and maintained there?

tilemill-project#2578

/cc @florianf @tmcw

[florianf]

I wouldn't just merge all changes back, since I removed a lot of stuff in this fork that I can't maintain, most important the whole native packaging.

Things worth merging IMHO:

• Added layer selection to map panel for fast comparisons with OSM and to save render time for low zoom levels
• Added search field to layer panel
• Increased size of layer panel
• Remember last selected folder in new layer dialog
• Better compatibility with kosmtik, TileOven mml project files should work out of the box with kosmtik (https://github.com/kosmtik)

[csytsma]

@florianf I'd like to revisit this, if you're open to it. Could we schedule a time to discuss it?