[IMP] move operators to field classes, add datetime field stub
[IMP] move operators to field classes, add datetime field stub

--HG--
extra : convert_revision : xmo%40openerp.com-20110331120627-fy6qnoor0w1fdefw


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