Bug 21751: Replace fixFloat with HC-sticky to fix Chrome display

Bug 21751: Replace fixFloat with HC-sticky to fix Chrome display

This patch replaces the fixFloat jQuery plugin with a new one: HC-sticky
(https://github.com/somewebmedia/hc-sticky). This plugin provides the
same functionality without the page-reflow problems fixFloat suffers
from.

To test, apply the patch and regenerate the staff client CSS. Test the
behavior of the floating toolbar on these pages:

 - Acquisitions -> Vendor -> Vendor details
 - Acquisitions -> Vendor -> View basket
   - On both these pages, test toolbar behavior before and after
     expanding the "Orders search" options at the top of the page.
 - Administration -> System preferences
 - Authorities -> Create or edit an authority
 - Catalog -> Advanced search
   - Search results
 - Catalog -> Item search
 - Cataloging -> Add or edit a record
   - Open the plugin window for the 008 field
 - Tools -> Label creator -> New label batch -> Add items -> Search ->
   Results
 - Patrons -> New patron
   - Test before and after expanding the patron search options at the
     top of the page
   - Test editing a patron too
 - Tools -> Automatic item modifications by age -> Edit
 - Tools -> Notices & slips -> Edit
 - Lists -> View list

Check that the About page has been updated with information about the
plugin.

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>