Make panels collapsible (#239)

* Make panels collapsible

- Add Panel component with collapse logic
- Use the component in all the necessary panel groups

* Remove unnecessary container from PanelCanvas

* Add "hide property" to Pane component to hide Panel contents using a prop

- Instead of doing conditional rendering, pass the condition to Panel as props

* Change collapse icon rotation for closed

- Use one icon and use CSS transforms to rotate it

* Remove unnecessary imports from PanelSelection

src/styles.scss

@@ -30,6 +30,27 @@ body {
     margin: 10px 0 10px 0;
   }
 
+  .panel {
+    position: relative;
+    .btn-panel-collapse {
+      position: absolute;
+      top: -2px;
+      right: 5px;
+      background: none;
+      margin: 0px;
+      color: black;
+    }
+
+    .btn-panel-collapse-icon {
+      transform: none;
+      display: inline-block;
+    }
+
+    .btn-panel-collapse-icon-closed {
+      transform: rotateZ(90deg);
+    }
+  }
+
   .panelTools {
     display: flex;
     flex-wrap: wrap;