Prepare release 2.6.7
Added tag 2.6.7 for changeset 07ccceb35bf7
Increase version number
Fix typo in Period.write to check invoice sequence changes

It was introduced in changeset 90edc4984c69.
Patch from Jordi Esteve.

issue3567
review2461003
(transplanted from 77bd9c1bb110f5cb51771231d9912267f546b404)

--HG--
extra : transplant_source : w%BD%9C%1B%B1%10%F5%CBQw%121%D9%91%22g%F5F%B4%04