Add paint search to the palette form

[Bernardo-MG]

When creating a palette it can be useful searching for the names of the paints to use, and adding them with a single click.

I've been toying with this but seems that be too much work and add little. Study it better.

An option is having two buttons on the paint form:

• Add a blank paint
• Choose and add an existing paint

This is mostly useful to find paint names through their codes, and viceversa.

[Bernardo-MG]

Existing paints should be able to include hex codes.