[IMP] website_sale : Don't show shipping address when only services are into shopping cart.
[IMP] When no stock moves, change whatever you want, otherwise no change at all for UoM.  #3440 Enhancement request richard-willowit

The default UoM can only be changed when there are no stock moves (or only cancelled ones), but to any category.
The purchase UoM can be changed whenever you want, but has to be in the same category as the default UoM.

Closes #3440

[IMP] When no stock moves, change whatever you want, otherwise no change at all for UoM.  #3440 Enhancement request richard-willowit

[FIX] Remove line

[FIX] Constraint should be applied when UoM or PO UoM is changed
[ADD] sale: option to install sale_layout from settings menu
[ADD] Add the website_links module.

This module tracks clicks in mass mailing mails and allow the generation of trackable links in a website interface.

Modules modifications
---------------------
Refractoring of the crm_tracking_* classes in a new module.

* Extract the crm_tracking_* from the crm module into a new module "utm"
* Remove the crm_mass_mailing bridge module
* New dependencies of mass_mailing and website_links to utm.
[ADD] stock: display UoM in stock quants
[IMP] base, ir_sequence: removed ir.sequence.type object, added test for ir.sequence.date_range, refactored ir.sequence and ir.sequence.date_range implementation
[IMP] crm: change label of 'probability' field and display 'Customer' in search instead of 'Partner'
[FIX] CRM dependencies
[ADD] product: allow to reorder product attributes
[FIX] website_quote: enable translation for signature modal

Adding <span>'s inside the <p> will allow the translation editor to
distribute the right branding on the strings to be translated.
[ADD] website_slides: new module doing stuff. I swear.

Courtesy of a lot of people including Mantavya Gajjar(mga-odoo), Ravi Gadhia(rga-odoo),Vijay Patel(vip-odoo), Pariket Trivedi(ptr-odoo)
[REVIEW] Pre-merge review. This commit will have to
be squashed, but not before the end of the review process.