Fix a few issues with sellable markup:

- When setting the markup, the new sale price should be rounded to two digits.
- When using the price editor, changing the price should update the markup,
  but when the markup is updated (after this price change), the price would
  be updated again.

Change-Id: I861bc4191f440c9d91d787d6e1e61a45f438cf35
Support ICMS CSOSN 900.

Also, if the sale was emitted in the ECF, dont export the full icms details,
just the required information.

This is done so the shop don't have to pay the taxes twice - one for the
ECF, and another for the NFe.

Change-Id: Ibe6aa29b9aea90408cc6980c74a67f2b187f372c
Do not validate client CNPJ when confirm a sale.

When confirm a sale using NF-e plugin, is not necessary validate the CNPJ.
 - That case already occurs with CPF, where the .txt file is generated normally even if client CPF is blank.

Change-Id: Icbc5a9a2b00359424214a1aeb9c136f2dfa755e7