[ADD] purchase and purchase requisition generic improvements
(../generic-addons/ rev 10.1.1)
[REVIEW] reviewed feature branch: pep8, styling, rewrite of intricate methods, licenses, ...
(../generic-addons/ rev 10.1.3)
[FIX] wrong company name, missing license, missing coding, wrong indentation for brackets (pep-8)
(../generic-addons/ rev 10.2.1)
[IMP] do not override completely the warehouse_id field, instead prefer to replace the only attribute to modify
(../generic-addons/ rev 10.2.2)
[FIX] pep8: space after commas, spaces around operators, cut long lines; use orm.Model rather than osv.Model
(../generic-addons/ rev 10.2.3)
[FIX] empty list evaluates as False
(../generic-addons/ rev 10.2.4)
[FIX] intricated condition
(../generic-addons/ rev 10.2.5)
[FIX] return early when the condition is evaluated to False to simplify the reading flow
(../generic-addons/ rev 10.2.6)
[FIX] unclosed literal
(../generic-addons/ rev 10.2.18)
[IMP] moved purchase modifications to the right module
      [IMP] improved bid workflow
(../generic-addons/ rev 15.5.1)
[FIX]purchase_extended: use rfq/po type in menu actions to differentiate cancelled rfq/po
(../generic-addons/ rev 15.5.3)
[IMP]purchase_extended, purchase_requisition: documentation
(../generic-addons/ rev 15.5.9)
[ADD]purchase: reason for cancellation + few fixes
(../generic-addons/ rev 15.5.10)
[FIX]purchase: repair after rebase + fix draftpo to cancel
(../generic-addons/ rev 15.5.11)
[IMP]purchase, purchase_requisition: add state draft bid for registering bids in case of open call for bids + add check call for bids has lines when confirming
(../generic-addons/ rev 15.5.13)
[FIX]purchase: renamed cancelled into canceled
(../generic-addons/ rev 15.5.14)
[FIX]purchase: fixed cancel reason unlink method
(../generic-addons/ rev 15.5.15)
[FIX]purchase: replaced osv.except_osv by orm.except_orm, osv.osv by osv.Model, osv.osv_memory by osv.TransientModel
(../generic-addons/ rev 15.5.16)
[FIX] pep8
(../generic-addons/ rev 15.5.17)
[ADD] YML tests + few fixes
(../generic-addons/ rev 15.5.20)