Fix expand slot components are not in the vue tree

This makes any vue global property inaccessible within the expand slot (eg: try accessing $store within the expand slot and you'll get undefined)

src/components/vsTable/vsTr.vue

@@ -108,9 +108,7 @@ export default {
       } else {
         tr.classList.add('tr-expandedx')
         let trx = Vue.extend(trExpand);
-        let instance = new trx();
-        instance.$props.colspan = this.colspan
-        instance.$slots.default = this.$slots.expand
+        let instance = new trx({parent: this, propsData: {colspan: this.colspan}});
         instance.vm = instance.$mount();
         var newTR = document.createElement('tr').appendChild(instance.vm.$el);
         this.insertAfter(tr, newTR)