Migrate *all* photos to the cavelab setup. Header/footer still broken.

Completely remove the other image gallery themes.

I now have: image galleries, with lightboxes, and captions, with links
in them (and to Hugo pages), with full images lazy-loaded, with all
thumbnails auto-generated, and the ability to do this on both
individual images *and* with globbing, from page resources, from this
page or any specified one.  See cavelab_notes.txt.

It also has the ability to use Exif data of the photo - if I
preprocess it into a JSON file.

Known issues:
- The theme header/footer are now being overridden.  I am working to
  fix this first.
- I am missing some kind of fonts/images needed for the lightbox to
  show up properly.

layouts/partials/footer.html

@@ -0,0 +1,8 @@
+<!-- From https://blog.cavelab.dev/2021/04/photo-gallery-posts/ -->
+
+{{- if and (eq .Type "photos") (eq .Kind "page") -}}
+  <script src="{{ (resources.Get "assets/lightgallery.min.js" | fingerprint).Permalink }}"></script>
+  <script>lightGallery(document.getElementById('lightgallery'), {selector: '.photo-item'});</script>
+{{- end -}}
+
+<!-- lightgallery is: https://github.com/sachinchoolur/lightGallery -->