Bug 16549 - Remove the use of "onclick" from header search forms

Bug 16549 - Remove the use of "onclick" from header search forms

This patch removes the use of "onclick" from all header search forms for
the purpose of triggering the "keep_text" function. This behavior is now
handled in the globally-included JS file.

To test, apply the patch and clear your cache if necessary.

- Enter text in any header search form field. Click to each other tab
  in the header and confirm that your text is copied to each.
- Test the behavior of the header search form on at least one page where
  each is included:

  - The staff client home page
  - The advanced search page
  - The authorities home page
  - The administration home page
  - The cataloging home page
  - The checkin page
  - The circulation home page
  - The patrons home page
  - Acquisitions -> Vendor -> Contracts
  - Administration -> Cities
  - Administration -> Currencies and exchange rates
  - Administration -> Patron categories
  - Administration -> Printers (why is this page still around?)
  - Administration -> System preferences
  - Administration -> Z39.50/SRU servers
  - Tools -> Notices & slips

This patch modifies does not fix the existing (unreported) bug which
prevents the keep text function from working in the include file used on
these pages:

  - Acquisitions -> Vendor -> Basket -> New order from suggestion
  - Administration -> Budgets
  - The serials home page

Signed-off-by: Claire Gravely <c.gravely@arts.ac.uk>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>