Added a popup to display event details to the programme shortcode

Made some adjustments to the render_programme_table method to include a link
with each event listed.
Added programme.js to call the event details page in a popup window.

Note: for this to work, the main FSESU theme had to have a new Event Details
template added and the site needed a new page added at /event-details/ that uses
the Event Details template
Added new form of display for the programme shortcode (upcoming)

Added a filter to allow shortcodes to be executed in widget_text
Added new function render_programme_upcoming and linked to the programme shortcode
Added new function get_programme as a centralised location to get the programme
details
Slightly modified the programme styling to give a vertical alignment in the
middle of table cells
Added new form of display for the programme shortcode (planner)

Added new function render_programme_planner
Added new function get_event
Updated programme.css to include additional styling for the planner