Added centralised script & stylesheet enqueuing functionality

Adjusted the main FSESU\Plugin class to include scripts and styles arrays
Added add_script and add_style functions so the enqueue_scripts only needs to be
fired by the main class. All other components need to add their scripts and
stylesheets to the arrays in the main class using the public functions added
Added stylesheet for the Programme Custom Post Type

Setup the basic styles for displaying the programme table this time around
Updated main plugin class to allow for admin styles and scripts
Made changes to the datepicker initialisation and theme to better suit the site