Improve filterability of title and caption
Allow control of forced image links

Prior to this, all galleries were linked to the image file, for the lightbox to work. This should be filterable, in case something else is desired.
Remove use of extract()
Convert manual minification to automatic
Remove the pointless lgljl_html5_shortcode_output filter
Break out some stuff to separate methods for scannability
Minor formatting consistencies
Follow WP 3.9 and add inline docs for hooks
Add @since tags to hooks
Some missed formatting tweaks
Update version to 2.3.0. Update documentation.