Convert the plugin into a "Must Use" one

[dharmann]

I've made a small change to the plugin, so to be able to use it as "Must Use" plugin.
For who's interested, I've moved the file plugin.php in the root folder of mu-plugins and renamed it like the plugin's folder: "wp-plugin-dependencies.php". After that, I've edited the including path in that file to reflect the new position...it seems to work.