Bug 11425: Add item search form in staff interface

Bug 11425: Add item search form in staff interface

Item search is available at catalogue/itemsearch.pl (link is in
catalogue/search.pl)
It only uses SQL (not Zebra)
* Use DataTables and server-side processing to be able to filter on
  individual columns after the first search is done.
* Allow to export results in CSV
* With Javascript disabled, search form still works (and CSV export too)

There is the possibility to define "Custom search fields" in a new admin
page admin/items_search_fields.pl (link is in admin/admin-home.pl)
A custom item search field is defined by:
* a name: its unique identifier
* a label: the text displayed to the user
* a MARC field/subfield: the field/subfield to query (it uses
  ExtractValue)
* an authorised values list (optional): if defined the list is displayed
  in the search form

New Perl dependency: Template::Plugin::JSON::Escape

Test plan:
1/ Apply the patch and run updatedatabase.pl
2/ Go to advanced search (staff interface), then click on "Go to item
search"
3/ Play with the search form! :)
In the 3rd fieldset you can add as many fields as you want and combine them with
boolean operators (AND, OR). You can use SQL jokers characters (%, _)
You can output to screen (in a DataTables table) or to a CSV file.
4/ In the DataTables table, play with filters and try sorting columns.
5/ Disable Javascript (with Firefox: extensions NoScript or YesScript,
or in about:config 'javascript.enabled' = false
6/ Reload the search page and do some searches on screen output. (there
is no sorting or filtering features, but there is still pagination)
7/ Try again CSV output.
8/ You can re-enable Javascript.
9/ Go to Administration > Items search fields
10/ Add a new field. Example for title (in UNIMARC):
  Name: title
  Label: Title
  MARC field: 200
  MARC subfield: a
  Authorised values category: None
(add another field with an authorised values category to see the
difference).
11/ As you are there try to update and delete some fields.
12/ Go back to items search form. You can see in the 3rd fieldset that
your fields have appeared in the selects.
13/ Try searching on them.
14/ I think you're done :)

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described. Good new option.
No koha-qa errors

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>