This is preparation for enabling an eslint indentation configuration.
90% of these changes are just fixes for indentation errors that have
snuck into the codebase over the years; the others are more
significant reformatting to make eslint happy (that are not otherwise
actually improvements).
The one area that we do not attempt to work on here is the
"switch/case" indentation.
This commit adds support for '+' and 'Z' for "zoom in" and '-' and 'z'
for "zoom out" shortcut keys in the lightbox image viewer for Pan and
Zoom.
Fixes: #8689.
This fixes the lightbox zoom issues that occurred on some browsers
due to the units of `deltaY` being in lines rathern than pixels,
making it incredibly slow to zoom.
This makes the canvas zoom and pan feature cross-browser compatible in
a few ways:
1. Replace deprecated `mousewheel` event in favor of the similar and
cross-browser event `wheel`.
2. Create approximate substitute for `e.movementX` and `e.movementY`
values that are missing in Safari.
