[FIX] l10n_pe, base_vat: Finish prepration for l10n_pe_edi

- base_vat: Correct management of the check of peruvian VAT without prefix.
- l10n_pe: Correct income account the last one is not correct.
- l10n_pe: Forced Round globally for peruvian companies once l10n_pe is
installed, and with the onchange.
- l10n_pe: For peruvian companies it does not make sense a sequence per
year and the year in the prefix is incorrect, we must force XXX- as
a sequence prefix.