[UI] Show a "Remove Color Swatch" Button on the Color Palette UI

[Jose-Moreno]

--Issue Summary--

Currently there's only an "add swatch button", so organizing custom palettes for different projects is really cumbersome.

--Video or Image Reference--

[MrStevns]

So i've started working on this: the implementation will be as following:

One can:

• delete a color using the delete button

• Select multiple colors to be deleted, by dragging or holding the equivalent button on the keyboard to select multiple
  

• right-click where as a context-menu will appear with three options:
  

This goes into a bigger implementation of making the color palette static, as in not connected to strokes or anything, and adding a new window to keep track of "connected" colors for the vector layer.
You can read more about my proposal here #962

[Kaikogf]

Very nice implementation
👍

[MrStevns]

Implemented and available in latest nightly build, closing.

[Jose-Moreno]

It's working well. Good job! 🙂