Moving the require of wp-admin/includes/plugin.php global init instead of only in Mock Buddypress

This way other components can call is_plugin_active() to check if BuddyPress is active
Configuring usable permalinks when BuddyPress isn't active
Renaming mock-buddypress.class.php to mock-buddypress.php

It's not a class, so naming it with .class was a mistake.
Set the current group ID correctly on the standalone courses screen

Previously it was just set to 0, which led to all lectures being displayed on the course screen. Now that it's pulling the actual group id, only lectures attached to that group are displayed.
Changing load_courseware_css hook to wp_enqueue_scripts

This lets it run when BuddyPress isn't activated, without changing the current behavior when BuddyPress is active.
Adding [courseware-dashboard] shortcode
Adding class and function stubs for the Dashboard