update _render_attribute / _render_relation prototype to gain more control on label through uicfg (for attributes and relations). Keep bw compat for crm/iliane

when fields are displayed in a table and label should'nt be displayed, set colspan to 2 on the field value cell

fix format string

cleanup

fix workflow consistency: check state/transition name uniqness in the wf when state/transition name is modified ; use the new msg argument of rql constraints to have a nicer error message on failure

nicer __str__ and __repr__ methods on rql constraints

refactor so that we can specify an extra argument to constraints which will be used as error message