[FIX] Error when selecting filters in calendar view
[FIX] Error when selecting filters in calendar view

e.g. calendar view of customer invoice

Also attempted to make the code flow slightly simpler by just forcing
the filter to a [value, label] pair in all cases.


havt/openerp-web,havt/openerp-web,akretion/openerp-web,havt/openerp-web,havt/openerp-web,akretion/openerp-web,akretion/openerp-web,havt/openerp-web