[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)
[FIX] wrong company name, missing license, missing coding line
(../generic-addons/ rev 10.2.7)
[FIX] orm instead of osv, orm.Model instead of osv.osv and except_orm instead of except_osv (deprecated)
(../generic-addons/ rev 10.2.8)
[FIX] pep8: space after commas, spaces around operators, cut long line, too short variable name; removed dead code
(../generic-addons/ rev 10.2.9)
[CHG] set item instead of update() when updating only 1 item, much more efficient
(../generic-addons/ rev 10.2.10)
[FIX] intricated condition
(../generic-addons/ rev 10.2.11)
[FIX] early return instead of nesting all the method
(../generic-addons/ rev 10.2.12)
[FIX] public method are not allowed to return None
(../generic-addons/ rev 10.2.13)
[FIX] assert the requirement of only 1 id when the ids can be a list or tuple instead of just taking the first one, which can be a misleading behavior
(../generic-addons/ rev 10.2.14)
[FIX] typo: 'canceled' with 1 'l' tends to be the used form in US
(../generic-addons/ rev 10.2.15)
[FIX] simplify really intricated method, it was hard to read and to understand what it was doing
(../generic-addons/ rev 10.2.16)
[FIX] typo: openerp.osv not openerp.orm of course
(../generic-addons/ rev 10.2.17)
[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_requisition_extended: add button to view generated po and fix button to view rfq/bids
(../generic-addons/ rev 15.5.4)
[IMP]purchase_requisition: At PO generation, cancell only rfq not the bids
(../generic-addons/ rev 15.5.5)
[IMP]purchase_requisition: rename button Done into Generate PO
(../generic-addons/ rev 15.5.6)
[FIX] after rebase and code review
(../generic-addons/ rev 15.5.7)