Bug 29960: Remove Modernizr dependency in the OPAC

Bug 29960: Remove Modernizr dependency in the OPAC

This patch refactors the code around JavaScript-driven responsive
behavior in the OPAC. The use of Modernizr dropped and the dependency
removed.

This patch also adds a missing listing for Enquire.js licensing on the
"About" page.

To test, apply the patch and perform a catalog search in the OPAC.

- Narrow your browser window until its width falls below 609 pixels
  (Using your browser's Responsive Design Mode is helpful for this, e.g.
  https://developer.mozilla.org/en-US/docs/Tools/Responsive_Design_Mode)
- The window should automatically scroll to the "main content" area, in
  this case the section headed by "Your search returned..."

- Change your browser window's width until it falls below 768 pixels.
- Scroll to the bottom of the search results where you should find the
  "Refine your search" facets box collapsed.
- As you increase your browser width above 768 pixels the facets box
  should expand.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>