Collections user balance API / batch file output

Collections user balance API / batch file output

New API open-ils.collections.user_balance_summary.generate,
which generates summary information on patron balance owed for all open
transactions that occurred at the requested location.  Optional flag
supports including per-xact summary information as well.  The summary
information is written to an XML file and placed in a protected, shared
web directory for download after the file has been generated.

During creation, the output file will have a .tmp suffix, allowing
clients to poll for file completion.

Includes a new opensrf.xml app_setting for open-ils.collections to
specifiy the batch file directory as well as a sample Apache config in
eg_vhost.conf

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>