Pick unused entities for lovelace cards (#3614)

* Pick unused entities for lovelace cards

* Type

* Table layout for unused entities

* properties

* remove unused import

* mwc-button

Need to find a way to set the color

* add icons to pick view dialog

* Comments

* Lint

* Restore unused entities for yaml mode

* Remove _elements

* decorators, types, comments

* flexbox + comments

* remove unused import

src/components/ha-checkbox.ts

@@ -0,0 +1,20 @@
+import { Constructor, customElement } from "lit-element";
+import "@material/mwc-checkbox";
+// tslint:disable-next-line
+import { Checkbox } from "@material/mwc-checkbox";
+// tslint:disable-next-line
+const MwcCheckbox = customElements.get("mwc-checkbox") as Constructor<Checkbox>;
+
+@customElement("ha-checkbox")
+export class HaCheckbox extends MwcCheckbox {
+  protected firstUpdated() {
+    super.firstUpdated();
+    this.style.setProperty("--mdc-theme-secondary", "var(--primary-color)");
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "ha-checkbox": HaCheckbox;
+  }
+}