Use Quartz scheduler

* Replaced the Spring scheduler with the Quartz scheduler. Spring's
TaskScheduler doesn't always play nice in shared environments that use
Quartz

* Moved the scheduling bean to the
"com.ushahidi.swiftriver.core.scheduling" package

* Sample context configuration file for the API

* NOTE: Spring 3 is not yet compatible with Quartz 2+. Therefore
use Quartz 1.8.x