[FIX] account: partner balance general totals

General totals were not computed at all, due to the condition "if not self.ids" which was always true as self.ids wasn't set.

Besides, a parameter allows to display only partner with balance greater than 0, which was completely ignored by the totals computation methods: The totals always included all partners, even those having balance equals to 0
Merge branch '7.0' of https://github.com/odoo/odoo into 7.0-win32