[IMP] improve css of tree_grid a tag.
[IMP] improve css of tree_grid a tag.

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