Add users the ability to bump ClassiPress ads back to top.
This will drive posters to come back to your site to bump their ads
and will help your site to look more active by ads changing all the
time even though many could be bumped ads.
Users are limited to bump at interval times and can be charged for it.
Admins can bump any ad any time without charge.
The charge is done through the framework payment gateways.
Bump packages are supported in ClassiPress 3.4+
