remove all useless header comments (#3363)

see #3358

used command: `find ./ -type f -exec perl -i -0pe
's/\/\*\s*magicmirror.*?\*\/\s*//si' {} \;`

This is a first draft, I think we should preserve some of the comments.

js/app.js

@@ -1,10 +1,3 @@
-/* MagicMirror²
- * The Core App (Server)
- *
- * By Michael Teeuw https://michaelteeuw.nl
- * MIT Licensed.
- */
-
 // Alias modules mentioned in package.js under _moduleAliases.
 require("module-alias/register");