Twenty Fourteen: Change to just one footer widget area and use Masonry

[anonymized_8769252]

As noted in #24858, the footer sidebar of the Further theme should be converted to use only one widget area, with jQuery Masonry handling the vertical alignment of the widget.

A patch with a first pass at this will follow soon.

[obenland]

Nice patch Frank! Some minor nit picks that would make it beyond great:

• We try to not use IDs as selectors, to make it easy to override them.
• Let's call it a 'Footer Widget Area' as it is not really a sidebar.
• Single line if/else blocks can omit braces for brevity (​#)
• I think we can optimize the masonry selector to be just #footer-sidebar.

[anonymized_8769252]

Thanks Konstantin for looking at the patch.

I updated it to fix the points that you outlined.

[lancewillett]

In 25065:

Twenty Fourteen: change to just one footer widget area and use Masonry JS to display the widgets in columns. Props Frank Klein, closes #24874.

[nacin]

In 25190:

Be less verbose when erroring out in do_feed() for an invalid feed template. fixes #24874.

[SergeyBiryukov]

[25190] was for #24784.