There can be multiple reasons for not grouping payment lines:
* The customer needs each payment line individually for matching references.
* For avoiding the risk of returning a big amount.
* For not overpassing amout limits.
* ...
So with this commit, you have the possibility of selecting at payment mode
level if you want to group or not
We drop the bank statement related part and we manage
the state of payment order with workflow transitions
triggered by the reconciliation of moves lines on the
transfer account.
