Bug 11622 - Add ability to pay fees and fines from OPAC via PayPal

Bug 11622 - Add ability to pay fees and fines from OPAC via PayPal

This patch adds the ability for a logged in user to pay fines and
fees from the OPAC via PayPal.

Test Plan:
 1) Apply this patch
 2) Create a paypal developer account
 3) Create two test accounts, a Personal account and a Business account
 4) Enable PayPal in Sandbox mode via the system preferences.
 5) Enter the business account API credentials into the new system
    preferences.
 6) Create a new patron, add some fines/fees
 7) Log in as that patron in the OPAC
 8) Choose to pay via PayPal, log in as the sandbox Personal account
 9) Complete the transaction
10) Note the fee is now paid

Signed-off-by: Carol Corrales <ccorrales@losgatosca.gov>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>