Bug 11876 [Follow-up] Add a diff view to staged MARC Records

Bug 11876 [Follow-up] Add a diff view to staged MARC Records

This follow up makes some corrections to the previously added files and
adds some functionality to the diff: A Javascript diff plugin highlights
the differences between the records in the two columns.

Corrections made: Converted tab indentation to spaces, corrected GPL
statement.

File organization: Moved showdiffmarc.pl and .tt to /tools/ to match the
location of the page with which it functions,
tools/manage-marc-import.pl. Corrected permissions on showdiffmarc.pl
accordingly.

Updates to the template: Added standard includes inclucing header menu
and breadcrumbs; converted custom layout to YUI Grid standard.

To test, follow the test plan previously defined:

- Stage a MARC record batch which contains at least one record match for
  something already in your catalog.
- Locate the staged MARC record batch in Tools -> Manage staged records
  and click to view the contents.
- Find the record which matched an existing record and click the "View"
  link in the Diff column.
- The compare screen should include the header menu and breadcrumbs. The
  differences between your staged file and the existing record should be
  higlighted.
- You should be able to return to the MARC batch you were previously
  viewing by following the link in the breadcrumbs or the link at the
  bottom of the page.
- Confirm that the "About" page includes information about the new
  JavaScript plugin on the Licenses tab.

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>