[IMP] account/sale/sale_layout: standardization of Quotation/Sale Order/Invoice printed layout + add missing information

- Column alignment and order are now uniform across those reports.
- Display Due date on invoices.
- Display payment term and fiscal positions notes.
[IMP] graph view on contacts
[FIX] sell future events only, not old ones
[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
[MIG]CRM: Migrated CRM into new API.

[MIG]CRM: Migrated crm.lost.reason class.

[IMP]CRM: Adding new field in report as per master file.

[MIG]CRM: Manage decorators and remove extra space and print.

[IMP]CRM: Managed decorator.
[IMP] CRM: Improve code.
[IMP] improve code
[IMP] use ensure_one
[IMP] improve code
[IMP] set proper indentation
[IMP] improve code
[IMP] set proper indentation
[IMP] improve code
[IMP] set proper indentation
[IMP] improve code
[IMP] improve code