Further organization of the browser scripts.

Moved server selection styles to launcher.css, as they are nearly finished.
Moved overlay convenience functions to overlay.js.
Moved launch area (landing.ejs) convenience functions to landing.js.
Various cleanups and documentation also added.

app/assets/js/scripts/welcome.js

@@ -1,7 +1,7 @@
-// DOM cache.
-const welcomeButton = document.getElementById('welcomeButton')
-
-welcomeButton.addEventListener('click', e => {
+/**
+ * Script for welcome.ejs
+ */
+document.getElementById('welcomeButton').addEventListener('click', e => {
     $('#welcomeContainer').fadeOut(500, () => {
         $('#loginContainer').fadeIn(500)
     })