Use Bower for jQuery, Bootstrap 3, Colorbox; fix #1205 -- internationalize Colorbox.

In order to make stuff easier to maintain, this makes us go more modern, and we now get to use Bower to update stuff.

Install Bower with:

    $ sudo npm install -g bower

Update stuff with:

    $ bower update

Much easier than before!

(warning, changing templates is still mandatory for CDNs.)

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Colorbox is now using locales (Issue #1205).

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A stray imagesloaded plugin has been removed.  It was not used by anything in Nikola.  In case that’s incorrect, there is a Bower treatment to apply for it.