[FIX] point_of_sale: uncrash widget.js

Error during forward port
[IMP] project: onboardin / usability improvements

- project kanban view: dashboard-like view, add sparklines for open tasks
and closed issues
- project: cleaned demo data, less stages
- project: description is now an html field
[FIX] res_users: set login_date as datetime instead of date

To allow display the login date according to the timezone of the user
[IMP] project: project alias generation is True by default.
[IMP] project: better diplay of task/issue title
[ADD] Add an html compressor option in website settings
[IMP] CRM Onboarding improvement
[IMP] sale_stock: warehouse_id field on sale order is now readonly, except in draft and sent states.
[IMP] accounting: modify writeoff_amount display in payment wizard
[FIX] website_mail & calendar: demo data break the layout of mail design
[FIX] website_mail: can't be edit the mail template, javascript must be added into the asset
[FIX] website: remove multi consecutive dropzone
[FIX] snippets: use the new API to define dropzone
Merge pull request #2547 from odoo-dev/master-fix-mass-mailling-snippet-chm

[FIX] website_mail: can't edit mail templates
[IMP] product: remove UoM constraint from product module and give it in stock and account module

Closes #2440
[IMP]Website_blog:implement new features rss feeds