[ADD] added rating, rating_project and rating_project_issue module

 - Task : https://www.odoo.com/web#id=8060&view_type=form&model=project.task
 - Pad : https://pad.odoo.com/p/r.2BmKqyvcwKbiXPRI

[IMP] Added option to install rating module under Project

[IMP] added template to display when customer rates the task/issue

[IMP] Improved template and code

[IMP] : rating , rating_project and rating_project_issue as per new api

[IMP]: rating template

[FIX] : test case failed

[IMP] : code
- put a domain on that one, otherwise the template rendering mechanism will fail
- put a different name and help; this is a rating_template_id, not a template_id. We already have some stage models having template_id that is a common template being sent to followers. Here it is a template linked to rating.
- are you sure this should be define on the stage ? if I set 3 templates on 3 different stages, will 3 different ratings be sent ? seems odd.