(css,js) Improve progress feedback

This ads a "ripple" effect that blocks the context when login in or
sending a message. Generic enough to be used elsewhere.

Fixes #3765

UI/WebServerResources/scss/styles.scss

@@ -66,6 +66,7 @@
 @import 'components/whiteframe/whiteframe';
 
 // Inverse components
+@import 'components/ripple/ripple';
 @import 'components/timepicker/timepicker';
 
 // @import '../angular-material/src/core/style/color-palette';