misc fixes for Thirdparty / addPerson

* set default values for ThirdParty in ThirdParty.vue
* set correct value for binding with phone (telephone instead of
phonenumber)
* add validation on ThirdParty/denomination: at least two characters, no
Null value

src/Bundle/ChillMainBundle/Resources/public/vuejs/OnTheFly/components/Create.vue

@@ -78,7 +78,7 @@ export default {
             case 'thirdparty':
                let data = this.$refs.castThirdparty.$data.thirdparty;
                data.name = data.text;
-               if (data.address !== undefined) {
+               if (data.address !== null) {
                    data.address = { id: data.address.address_id }
                } else {
                    data.address = null;