Change brand color and logotypes (#18592)

- Add rake task for generating Apple/Android icons and favicons from SVG
- Add rake task for generating PNG icons and logos for e-mails from SVG
- Remove obsolete Microsoft icons and configuration
- Remove PWA shortcut icons

lib/assets/wordmark.dark.css

@@ -0,0 +1 @@
+// Not needed

lib/assets/wordmark.light.css

@@ -0,0 +1 @@
+use { color: #000 !important; }