Created magnific-popup.css

Credit to @dimsemenov
Added magnific-popup.css call to header
Added script to initialise Magnific Popup

Refer to:
http://dimsemenov.com/plugins/magnific-popup/documentation.html
Tweaked lightbox styling (combines with defaults)
Checked for .popup-gallery before running magnific
Corrected indentation
Added arguments to Magnific Popup initialisation
Regenerated style.css