Revert "fixup! Adjust background and border styles to match Critic's jQuery UI theme"

This reverts commit 600101479b434f2a6f7f9408db921bf35c37c145.
Revert "Make optgroup headings stand out a little more"

This reverts commit 53dfc60834a5e30ccfe49795e833940b07a79969.
Revert "Adjust background and border styles to match Critic's jQuery UI theme"

This reverts commit f886adc547300822cd8d62a46f6143da99b0b0bf.
fixup! Add task for copying files committed in Critic's repository

Copy files to src/resources/third-party/ in the Critic repository