Introducing quartz as scheduling engine

Configuration and triggering regular tasks were suboptimal so this pull adds [quartz-scheduler](quartz-scheduler.org/) to the project along with a simple scheduler implementation which can be configured from spring xml configuration files. For metadata update update task this has been done in [spring-sos-config.xml](https://github.com/ridoo/SensorWebClient/blob/ff84622707a874f6d840d0dc7842b371af92b620/sensorwebclient-webapp/src/main/resources/spring-sos-config.xml#L17-L36).

Configuration can be done via `cronExpression` for regular tasks or --- if missing --- as one time running tasks as startup.