Better Color in Rich Text Box

[Gulix]

Following #194
The current Color control in the Rich Text Box allow the user to specify the color of the text.
The template must allow this behaviour. Also, the template can provide a closed list of colors or let the user choose any color.

Changes to be made :
-> Let the user choose any color, but provide a list of chosen colors in the first list
-> It should be possible to modify the background color also. Or just the background without the foreground.
->The default color of a text is displayed in black in the Rich Text Field. But can this color be variable on the canvas (for example, linked to a Color field ?) Can we provide a "Variable Color" in the Rich Text Field ?
-> The lists of colors should be different between the Foreground and the Background. The current control in CKEditor doesn't provide that.

Maybe this Issue will need to be separated in multiple issues. We'll see, depending on the need for future templates. It's currently on hold.