Started refactoring of the warranty limit method

In order to be able to use it in an onchange
onchange_invoice_id now compute the warranty limit
Extracted a method so it will be possible to add an onchange
onchange_invoice_id now get the values for the warranty address
When the product_id change, change the warranty infos as well
do not pass the claim id so the onchange use the values on the views

this is better since the values in the view could have been changed
trigger the onchange when the invoice line is modified too
Update warranty information when the date, the type or warehouse of the
claim is modified
pep8 in crm_claim_rma
reset values when some fields are missing to compute warranty
Merge branch 'rma-warranty-onchange' into qo-pending-merge-qa

From https://github.com/OCA/rma/pull/8
Trello:
https://trello.com/c/q8SZiijA/369-creation-de-cas-sav-et-gestion-des-retours