DataHub source for constant values
Some of the values in the DataHub
do not change over time. This may be simple configuration data or things that are considered to be constant, i.e. a fix position. To avoid re-implementing data sources over and over for different values, a generic source for constant values should be implemented that sets the value of a specific path at the beginning. It will most probably be limited to some well-known types but should cover the basic use cases. Furthermore, an option to periodically renew the timestamp should be provided as well.
The usage in the configuration file could look like this:
<Source Type="constant" DataType="double" Update="500ms" Path="/position/heading">0.0</Source>
Once #158 (closed) is finished, implement the source based on the defined interface.