UTCT-86: Make QR code plugin compatible with 404 plugin

[UTCGilligan]

For Bugfix release 1.5.1.

"Fix the other fix because it broke something else."

QR codes were broken by the 404 plugin, because the QR code was set to fire on a hook that runs after the hook used by the 404 plugin. Changed QR to use the same hook as the 404, at a higher priority (default 10, vs 999 for the 404 function), as suggested by YOURLS author, ozh.

• https://gotest.utc.edu/badshorturl (404)
• https://gotest.utc.edu/about.qr (good QR)

[UTCGilligan]

Looks good:

• change hook for QR plugin
• make the UTC word mark image load for all bad URLs, e.g. https://go.utc.edu/admin/bot-probing-for-exploit.php (404 is turned off in prod right now so QRs continue to work)... https://gotest.utc.edu/admin/bot-probing-for-exploit.php

[UTCbridget]

Looks great!