Bug 9009 - Add separate user js and css for SCO module

Bug 9009 - Add separate user js and css for SCO module

Add system preferences SCOUserCSS and SCOUserJS to define separate CSS and JavaScript for the Self Checkout Module.

Test plan:
1) Apply patch
2) Run updatedatabase.pl
3) Add something arbitrary to the new sysprefs SCOUserCSS and SCOUserJS ( such as TestCSS and TestJS ).
4) Load the SCO module in a browser, and view the HTML, verify the CSS and JS values in the system preferences have been included.

Signed-off-by: Marc Veron <veron@veron.ch>
I tested with an alert('hello') as JavaScript and some background-color for the CSS. Worked as expected.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>