[IMP] sales_team, web: add and improve color widget to improve UX on crm.tag

The color picker help the user to choose a color instead of picking it
by id.

The title and arial-label "no-color" default value are removed from the
picker_preview because they are not accurate. Instead name of currently set
color is used.

Task ID 2128166

closes odoo/odoo#47474

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>