When the user clicks on a pixel, all pixels of the same color are being selected. Shift adds to the selection, Ctrl subtracts. The icon and the hint tooltip are temporary.
Instead of having a gazillion icons for each tool and its blue-orange variations, which led us to create 4 different textures for each tool, now we only need one texture for each tool and each theme. The blue-orange background has been made into a different TextureRect for each button.
This makes it easier for people to create new tools. Now, each new tool requires 3 textures (to cover every theme), instead of 12(!). I'm hoping to bring the number down to 1 in a future commit, by automating the theme color converting process.
