General DateTimeBounds fetching

[FlorianFehring]

If a component uses data that contains time information it should be possible to request the start and end timepoint from the component.
This applies on two ways:

• 1. Fetch start and end timepoint of data avaialble in component
• 2. Fetch start and end timepoint of data available from source (e.g. REST)
• Use this to limit selectable date / time on aggregation / General use of timeframe
• Use this to create a "show all" button in components menue near the timeframe selection

Example code can be found at SmartMonitoringCustomisations/Airquality/ dateBoundFetcher.js