Pivot implementation and redesign (#69)

- Pivot support implementation 
- Rename queries into inquiries
- Rename editor into workspace
- Change result set format
- New JSON format for inquiries
- Redesign panels

src/views/Main/Workspace/index.vue

@@ -0,0 +1,62 @@
+<template>
+  <div>
+    <splitpanes
+      class="schema-tabs-splitter"
+      :before="{ size: 20, max: 30 }"
+      :after="{ size: 80, max: 100 }"
+    >
+      <template #left-pane>
+        <schema/>
+      </template>
+      <template #right-pane>
+        <tabs />
+      </template>
+    </splitpanes>
+  </div>
+</template>
+
+<script>
+import Splitpanes from '@/components/Splitpanes'
+import Schema from './Schema'
+import Tabs from './Tabs'
+
+export default {
+  name: 'Workspace',
+  components: {
+    Schema,
+    Splitpanes,
+    Tabs
+  },
+  async beforeCreate () {
+    const schema = this.$store.state.db.schema
+    if (!schema || schema.length === 0) {
+      const stmt = [
+        '/*',
+        ' * Your database is empty. In order to start building charts',
+        ' * you should create a table and insert data into it.',
+        ' */',
+        'CREATE TABLE house',
+        '(',
+        '  name TEXT,',
+        '  points INTEGER',
+        ');',
+        'INSERT INTO house VALUES',
+        "('Gryffindor', 100),",
+        "('Hufflepuff', 90),",
+        "('Ravenclaw', 95),",
+        "('Slytherin', 80);"
+      ].join('\n')
+
+      const tabId = await this.$store.dispatch('addTab', { query: stmt })
+      this.$store.commit('setCurrentTabId', tabId)
+    }
+  }
+}
+</script>
+
+<style scoped>
+.schema-tabs-splitter {
+  height: 100%;
+  background-color: var(--color-white);
+}
+</style>