[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

splbio/openerp-web,MarkusTeufelberger/openerp-web,gisce/openerp-web,MarkusTeufelberger/openerp-web,vnc-biz/openerp-web,splbio/openerp-web,vnc-biz/openerp-web,splbio/openerp-web,gisce/openerp-web,gisce/openerp-web,vnc-biz/openerp-web,MarkusTeufelberger/openerp-web,vnc-biz/openerp-web