Bug 8630: Adlibris covers (syspref files)

Bug 8630: Adlibris covers (syspref files)

This patch adds a system preference for cover images from Swedish
book retailer Adlibris. Images are retrieved via http or https
from an external web server. This might leak OPAC and Staff
interface data to third parties and should thus be used with
caution.

Sponsored-By: Halland County Library
Test plan:

Test 1: Test upgrade procedure for clean installation.

  Start by removing existing sysprefs, if present:

  $ mysql -u kohaadmin -p -D koha
  > DELETE FROM `systempreferences` WHERE `variable` LIKE 'Adlibris%';

* Apply this patch which will add a pref file, update the 'syspref'
  structure and add an atomic upgrade file.

* Install the update:
  Koha$ perl installer/data/mysql/updatedatabase.pl

* Once upgraded and logged in, Select 'More', 'Administration',
  'Global Preferences' and finally 'Enhanced content'.
  There should be a new option called 'Adlibris'.

  The first option should default to "Don't show", if not the
  patch is broken.

  The second options should show the default URL:
  http://www.adlibris.com/se/organisationer/showimagesafe.aspx

  If not, the patch is broken.

Test 2: Changing sysprefs

* In the control panel, change the first value from "Don't show"
  to "Show" and save the changes. Use MySQL client to inspect changes:

  $ mysql -u kohaadmin -p -D koha
  > SELECT * FROM `systempreferences` WHERE `variable` LIKE 'Adlibris%';

  The column 'value' should now have the value '1', if not the patch
  is broken.

Test 3: Apply update to existing data

* Re-execute the installer now that the database has the data already:
  Koha$ perl installer/data/mysql/updatedatabase.pl

  If any errors occur the patch is broken.

  Examine the database contents:

  $ mysql -u kohaadmin -p -D koha
  > SELECT * FROM `systempreferences` WHERE `variable` LIKE 'Adlibris%';

  If the values were overwritten by the installer the patch is broken.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>