[FIX] attempt at supporting inherited fields (through _inherits) as group_by in read_group()
[FIX] attempt at supporting inherited fields (through _inherits) as group_by in read_group()

gisce/openobject-server,ovnicraft/openerp-server,splbio/openobject-server,splbio/openobject-server,gisce/openobject-server,MarkusTeufelberger/openobject-server,vnc-biz/openerp-server,ovnicraft/openerp-server,splbio/openobject-server,MarkusTeufelberger/openobject-server,gisce/openobject-server,MarkusTeufelberger/openobject-server,vnc-biz/openerp-server,xrg/openerp-server,xrg/openerp-server