Add scale bars and rework UI

There were too many things in the column view.  Input title fonts,
frame rates and scales are now below and pertain to which ever input is
selected.  There are now nice handy ‘copy to all inputs’ buttons so you
don't have to enter the same information six times or whatever.

Also, this fixes a bug where ffmpeg would complain if an input's title
was empty (we just make the title a single space in this case!)

And yeah, scale bars.