[IMP] payment_acquirer, payment_acquirer_transfer

[IMP] payment_acquirer, payment_acquirer_transfer

- payment_acquirer: added base method for form-based validation
calling various model-dependant methods.

[FIX] payment_acquirer: fixed tx values not given to form to render
when having no custom method for a specific acquirer

- payment_acquirer_transfer: added form validation, using the new
acquirer method. Updated controllers. Updated generated form to include
tx details. Fixed method for form_action_url taht was missing.

bzr revid: tde@openerp.com-20131120140119-8zuvm2ypr5arvf5y