Fix for dupe/missing videoTimes/videoUploaded

Duplicate IDs are prevented by piping them into an object rather than an
array. Introduced a loop to ensure that multiple Youtube URLs on the
same page all get tagged, not just the last instance.
Night mode tweaks

Comment navigator background/close button background/hover
Night mode - standardize quotes

Replace the remainder of the double quotes with singles.
Night mode - restore zeroed right margin

I removed this in error for 4.2.0
Show the 'last edited' timestamp

Append the timestamp to the minutes/hours/days ago display without the
need to hover.
Merge pull request #367 from gavin19/master

Fix for Youtube dupes/missing videoTimes + night mode CSS