sale_order_partial_invoice - Some fixes and enhancements:

[IMP] Make readonly wizard non-modifiable fields.
[FIX] Check if the quantity to invoice is greater than the remaining one.
[FIX] Made a little hack to avoid the creation of counterpart invoice lines in subsequent invoices.
[FIX] Write 'progress' state manually when order is fully invoiced, because workflow doesn't do it.
[IMP] Open the resulting invoice after the wizard.
[FIX] Change type of name field to text to avoid format loosing.