[IMP] *: one Makefile to rules them all.

Create one unique generic Makefile to compile sass files.
[FIX] web,web_kanban: correct radial-gradient usage
[MERGE] forward port of branch 7.0 up to 3e3e35e
[MERGE] forward port of branch saas-3 up to ec27773
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64