Minor formatting changes and imports cleanup
Add prowl-api jar to the project

A follow-up change shall implement the sending of prowl notifications
and needs a jar which is not present on maven central. This change
creates a project-internal repository to allow using the jar as a maven
depdendency
Add support for sending Prowl Notifications

Prowl Notifications are push notifications sent to iOS devices with the
help of the 'ProwlApp' (http://www.prowlapp.com) and are nearly
instantaneous.