Layout drawing (#2232)

* - Show "Add" button in the toolbar when a display layout object is selected.
- Add a flag to object view's show() method to indicate immediate selection of the view. If the view implements getSelectionContext() use it, otherwise set to default context.

* Create a component for each element.

* Saving work

* Add element factory for creating new instances of elements.

* Mutate element when a new one added and get elements when the component is mounted.

* Add create() method for creating a new telemetry and element in their respective view configuration.

* Add some of the toolbar controls for box, text, image and line elements. Also, add X, Y, Width and Height controls for alhpanumeric elements.

* Pass name to addElement as type.

* Add c-frame-inspectable class if item is inspectable.

* Clean up

* Hide frame for summary widgets by default.

* Better styling for editing

- s-selected on shell__main-container;
- Better edit grid coloring for espresso;

* - Update toolbar-button to support dialogs.
- Update toolbar to construct a value object based on form keys if a toolbar item has a dialogi, and mutate the form keys.
- Add toolbar controls for editing text and url for 'Text' and 'Image' elements respectively.

* Editing-related changes

- Removed hard-coded .is-selectable and .is-moveable from
LayoutItem.vue, updates accordingly to _global.scss;
- Theme constants updated;
- TODO: apply changes to Flexible Layouts;

* Better defaults

- Better default grid size and object size;

* - Fix toolbar-input to read value as a number if type is 'number'.
- Remove rawPosition from view configuration and instead get the position and dimensions from the properties (x, y, width and height) directly.
- Set the style property on the view configuration instead of the layout item.
- Move the logic for updating the style to the view configuration.

* Fix default dimensions for telemetry items and subobjects since the default grid size is changed.

* Remove form definition for display layout type.

* Reword the comment

* Let subobject view configuration handle new panel creation.

* Add default grid size back and remove unused code.

* Pass in only the needed method.

* Define default position in case the object is not added via drag 'n drop.

src/plugins/displayLayout/components/LineView.vue

@@ -0,0 +1,56 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2018, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+
+ <template>
+  <div>
+    <svg :width="gridSize[0] * element.width"
+         :height=" gridSize[1] * element.height">
+        <line :x1=" gridSize[0] * element.x1 + 1"
+              :y1="gridSize[1] * element.y1 + 1 "
+              :x2="gridSize[0] * element.x2 + 1"
+              :y2=" gridSize[1] * element.y2 + 1 "
+              :stroke="element.stroke"
+              stroke-width="2">
+        </line>
+    </svg>
+  </div>
+ </template>
+
+ <script>
+    export default {
+        props: {
+            item: Object,
+            gridSize: Array
+        },
+        computed: {
+            element() {
+                return this.item.config.element;
+            }
+        },
+        mounted() {
+            this.item.config.attachListeners();
+        },
+        destroyed() {
+            this.item.config.removeListeners();
+        }
+    }
+ </script>