Clean up and extend framework interfaces

This is a followup to !133 (merged) and !134 (merged) towards a simpler framework. Includes:

• Undeprecated and extended IService interface that is intended to replace the specific IContextDecorator.
• Remove unused IReader::skip interface.
• Streamlined directory layout, e.g. Barcode is now in EventData, RandomNumbers in Framework.
• RandomNumbersSvc renamed to RandomNumbers since its not a service anymore.
• Use 64bit seed for random numbers.
• More code documentation of the interfaces and their intent; updated algorithm guidelines in the README.
• HelloWorld-like examples have been merged into a single one, that demonstrates the framework core functionality.

This MR in itself should not change any functionality. I expect a few additional MR in the future that continue the cleanup, but I wanted to get this already merged to avoid overly large MRs.