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/ChillThirdPartyBundle/Resources/public/vuejs/_components/OnTheFly/ThirdParty.vue

@@ -92,7 +92,7 @@
       <div class="input-group mb-3">
          <span class="input-group-text" id="phonenumber"><i class="fa fa-fw fa-phone"></i></span>
          <input class="form-control form-control-lg"
-            v-model="thirdparty.phonenumber"
+            v-model="thirdparty.telephone"
             v-bind:placeholder="$t('thirdparty.phonenumber')"
             v-bind:aria-label="$t('thirdparty.phonenumber')"
             aria-describedby="phonenumber" />
@@ -120,6 +120,11 @@ export default {
          //context: {}, <--
          thirdparty: {
             type: 'thirdparty',
+            address: null,
+            kind: 'company',
+            name: '',
+            telephone: '',
+
          },
          addAddress: {
             options: {