Improvement performance of validation the statement
When a account statement with number > 400 lines is validated, the time for processing is very long between 14-17 min, indeed the screen freeze this time, in many shops this number of sales/invoices is reached in a day, indeed the number of invoices can be greater.
I figured out this method 'create_move' to create a move for each invoice, maybe would be better add another option for process it.
http://hg.tryton.org/modules/account_statement/file/tip/statement.py#l456