Add extension example for DynamicTable

[oruebel]

To further enhance the extension tutorial it will be useful to create end-to-end examples for how to create extension for specific use cases. One such use case is extending the DynamicTable type to collect results from a new analysis algorithm (e.g., for feature detection) or to extend an existing type, e.g., TimeIntervals to define custom interval definitions.

See also #59 for an example