[FIX] account.payment / check writing / batch deposit :

- restored icon of modules account_check_writing and l10n_us_check_printing
- removed payment_type from account.payment tree/view since those views are already used with a domain and the type can be inferred from the name given by a sequence
- account.payment field company_id wasn't stored and, so, 'Group By' failed
- fixed extensibility of register payment wizard through method get_payment_vals()
- since register payment fully pays selected invoices, the amount should be readonly
- if payment journal is called 'Payment Mode', payment_method should not be called 'Payment Mode'
- improved batch deposit template
- check memo length when registering a check
- in check printing, sort invoices by due date
- checks get a check number attributes when registered from the payment wizard as well
- when a module extends a method from account.payment it should be careful to check the selected payment method