Add EventMediaLoader

Handles loading of URL previews and will handle all
matrix media messages types.

src/qml/utils.js

@@ -250,3 +250,9 @@ function copyToClipboard(text) {
     window.pseudoClipboard.selectAll()
     window.pseudoClipboard.copy()
 }
+
+
+function urlExtension(url) {
+    return url.toString().split("/").splice(-1)[0].split("?")[0].split(".")
+              .splice(-1)[0].toLowerCase()
+}