LP1492793: Support Application Name Postgres Option

LP1492793: Support Application Name Postgres Option

If app_settings/database/application_name is defined,
connections by that service will have the application_name
postgres option set, allowing log analyzers to associate
queries and services.

To test:

[1] Apply the patch and restart OpenSRF services.
[2] Query the pg_stat_activity table in the PostgreSQL
    database; the application_name column should now
    be populated with values like 'open-ils.cstore'
    or 'open-ils.storage' that indicate which Evergreen
    service holds the database connection.

Signed-off-by: Jason Boyer <jboyer@library.in.gov>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>