[FIX] account_payment: fixed the view of payment order to display the amount of transactions
[IMP] account_payment: remove dead voucher code and extension hook

Since bank statement do not use vouchers anymore in 8.0,
it's not necessary to create the voucher anymore.

Additionally, I add an extension point to let modules adapt
the statement line.
[IMP] doc: try to clarify what $as is in qweb doc
[FIX] website_forum:
   Use if_dom_contains to check if we need to load js
   Fix bug where _tag_to_write_vals was called like old API but model converter was new api
   Move IsKarmaValid and Load CKE only in website_forum context
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64