Make a HarvestSchedulerApplication that runs the HarvestScheduler

Currently the HarvestScheduler is embedded inside the dk.netarkivet.harvester.webinterface.DefinitionsSiteSection

It should have a application of its own to prevent excessive memory usage in the GUIApplication to bring down the Scheduler
and vice-versa.

However, this means, that the Harvester database can no longer be embedded, and must be started as its own server.

Of course those who uses MySQK and Postgresql as their DBMS already meets this requirement