switched to glide.js for image carousel

Two known bugs:
– The navigation dots don’t update on new slides; this was reported to
the author of glide.js and is now in the backlog for version 1.0.7; no
timetable
– In Chrome and Opera, after navigating away from home.php, when the
back bottom is used to return to home.php, the svg’s via <object> are
switched around. This is a known bug in Chrome (issue 352762) and is
resolved in Canary 36.0.1924.0; waiting to filter down to Chrome