[FIX] fleet: vehicle cost name field unhacked.

- remove name composition based on vehicle name, date and cost_subtype_id;
instead those fields have been added to the tree view. name field is now just
a related to the vehicle name, but the name field itself does not seem necessary
anymore. Should be checked further.

bzr revid: tde@openerp.com-20140217133930-dmzbwjtr58s4upy3