Add tags for brush list

Warning: two tags refuse to display , named "Ink" and "FX"
I think the strings are sort of blacklisted (from 3.x ?)

The list of tag is simple and list preset for suggesting categories
to the final user:

• Digital:

List all presets with a rendering only digital tools can does.

• Paint:

List a suggestion of presets to make textured/traditional paint.

• Ink:

Tools for the black&white artist (comic, manga, illustration).

• Pixel-Art:

Three tools for the pixel artist

• Sketch:

A list of preset to put down quickly an idea on the canvas. Contain
also all charcoal/pastel/pencil and other dry techniques.

• Textures

All the stamps and patterns in the library.

• My Favourites

A list of ten brush to plug in the right-click pop-up palette by default
and a generic name to encourage the end user to use it for his/her own
brushes.