[hub] Register components, init Item Page

- commonly used components are pre-registered
- add DetailHeaderItem component
- begin ItemPage

erpnext/public/js/hub/components/DetailHeaderItem.vue

@@ -0,0 +1,20 @@
+<template>
+	<p class="text-muted" v-html="header_item"></p>
+</template>
+
+<script>
+
+const spacer = '<span aria-hidden="true"> · </span>';
+
+export default {
+	name: 'header-item',
+	props: ['value'],
+	data() {
+		return {
+			header_item: Array.isArray(this.value)
+				? this.value.join(spacer)
+				: this.value
+		}
+	},
+}
+</script>