They're no longer TextureButtons, but Buttons with TextureRect as children. This makes it easier to make them work for multiple themes, and we also save some disk space.
More buttons will follow soon.
Folders "Brushes", "Palette" and "Palette/Custom" now get created if they don't exist (tested on Windows export).
Also, the palettes don't need the Default palette to work anymore, and Default along with bubblegum16 aren't copied to the Palette folder now.