Complete implementing popover system main features (#131)

* Make popover buttons open popover menus and add placeholder messages to all of them.
* Implement all directions for drawing, aligning, and edge-clamping popovers.
* Fix popovers so they are drawn outside their parent panel bounds and not clipped.
* Fix popover HTML to avoid nesting it inside a <button> element.

client/web/src/App.vue

@@ -21,6 +21,22 @@ button {
 	line-height: 1;
 	color: #ddd;
 }
+
+// For placeholder messages (remove eventually)
+.popover {
+	h1,
+	h2,
+	h3,
+	h4,
+	h5,
+	h6,
+	p {
+		margin: 0;
+	}
+	p {
+		margin-top: 8px;
+	}
+}
 </style>
 
 <script lang="ts">