Theme editor color palette improvements

We recently added a few additions and improvements to the Color Palette feature in the theme editor.

1. There is now a menu button (the 3 vertical dots) next to each color palette item that lets you insert before, insert after, move to first, or move to last position. While you can still drag items up and down, this is a nice addition when you're adding to a large list. Font palettes also got this feature.
2. Search the color palette.
   On the color palette section you can now search by the color value or the color label. Helpful when you have a lot of colors in the palette.
   You can also search the color palette when you're selecting a color in the color picker. When you choose the color palette option there is a search box at the top of the palette list that gets focus.
3. Add a color to the color palette from the color picker. 
   If you're editing a color elsewhere in the theme editor, you can now set that color to be part of the color palette right from the color picker. Go to the Palette section of the color picker and click on the "Add to palette" button at the bottom. You can set a descriptive name and set the display order (it defaults to last).
4. Edit an existing color palette color from the color picker.
   When you're editing a color elsewhere in the theme editor, you can update an existing color palette value to be the value from the color picker. Go to the Palette section of the color picker and click on the "Update a color" button at the bottom. You can then select which palette color to update.
5. Set a palette color to reference another palette color.
   If you've really taken advantage of the color picker then you may have a core set of colors and then reuse those colors in multiple palette colors. While this is fine, it adds more work if you ever want to change that core color. Now, a palette color can reference another palette color. When the parent color changes, all child colors are automatically updated, even when used in color pickers elsewhere. Up to ten levels of reference are supported, although that will get complicated to keep track of so we recommend trying to just link to a core set of colors.