Hyperlink and streamline author & committer information in the commit details pane in history view

Switch to a 2-rows layout and save tons of horizontal and vertical space.

• Instead of separating email addresses from author / commiter names, turn them into hyperlinks
• Show email addresses on hover with a tooltip
• Move the timestamps to the now reclaimed space on the right
• Adjust and harmonize the spacing between grid items
• Dim the committer line a bit to put the emphasis on the author

It looks roughly like this (same screenshot sizes):

Before	After

@TheEvilSkeleton kindly contributed the last commit on top of the branch, where we don't hyperlink commonly known automation-related email addresses like no-reply@, noreply@, gnome-sysadmin@ (the translations bot), localhost@, root@, etc.

Overall:

• This allows for a much more compact and aesthetically-pleasing UI. This fixes #440 (closed) and fixes #409 (closed) (by making it obsolete).
• This does not touch the commit creation dialog, I left the email addresses plainly visible / non-hyperlinked there.
• I did not align the date/time labels to the right because I'm not sure if you would like it and I want to get this merge request accepted with the minimum amount of changes to begin with. If you would prefer those labels to be aligned to the right, let me know and I can add a very simple commit on top to do that.