slimbox2 upgrade to fix problems with jquery

Patch for "master" branch: https://reviews.mahara.org/9056

Will move the photoframe option to be a block instance config setting rather than have it for all gallery blocks

Acceptance Criteria:

1. New toggle switch labelled - Use photo frame yes/no (Default = No) for Image galleries only

NOTE: photo frame is white only - border around image and a surrounding line a few pixels away to give illusion of a frame

Preconditions:

1. Authenticated user logged in
2. User has a folder of Images with the following
a. Some images have a description
b. Images vary in width and height from very small to very large

Test Script - user create a page and add an image gallery

1. Site admin login
2. Create a portfolio page and add an image gallery
3. Confirm that the modal window for "Image gallery: Configure" displays "Use photo frame" toggle switch ✔
4. Set the "style" to Thumbnails
5. Set "Show descriptions" = yes
6. Enable the "Use photo frame" toggle switch = Yes
7. Click the save button
8. Confirm that the Image gallery block displays images with a frame around each image ✔
9. Click the "Display page" button
10. Confirm that the Image gallery block displays images with a frame around each image ✔
11. Confirm that the Portfolio page with an image gallery and the "Use photo frame" toggle switch enabled displays correcly on the following
a. Chrome - Linux ✔
b. Firefox - linux ✔
c. MS Edge - win 10 ✔
d. IE 11 - win 10 ✔

Catalyst QA Approved ✔

Reviewed: https://reviews.mahara.org/9056
Committed: https://git.mahara.org/mahara/mahara/commit/66e7468ad0856faad3a029cc772e5b4572632ea8
Submitter: Cecilia Vela Gurovic (<email address hidden>)
Branch: master

commit 66e7468ad0856faad3a029cc772e5b4572632ea8
Author: Robert Lyon <email address hidden>
Date: Wed Aug 8 13:30:18 2018 +1200

Bug 1785938: Fixing gallery and changing slimbox2 to fancybox3

Things done with this patch:

1) Changed the 'Use photo frame' option from being a plugin variable
to being an instance config variable

2) Added back in the css for the giving the gallery images photo frame
borders

3) Get the non-square thumbs to render correctly spaced on load

4) Swapped the slimbox2 to fancybox3 and allowed the block itself to
control when to put content into head data

behatnotneeded

Change-Id: I397be45f2347588988b663b25b560d8ab876afe1
Signed-off-by: Robert Lyon <email address hidden>