refactor(trial_balance): Migrate trial balance to odoo 8.0
On odoo 8.0 is not possible to add new porperties to records as used to be able on openerp 7.0 that's why on OCA financial reports webkit are creating a new localcontext for hold values like initial balance, debit, credit and final balance that used to be added like property on records
Fix #67 (closed)