Support System.IO.Stream in Yarhl.IO classes

[pleonex]

Is your feature request related to a problem? Please describe.

In order to improve the compatibility of Yarhl with other frameworks, we should make easier to work with Stream and DataStream. Right now, if you start using DataStream, it's hard to use any framework that requires a Stream (including BCL). This will help users to start using Yarhl in their projects.

Describe the solution you'd like
We should make DataStream inherit Stream. It makes sense as it behaves like a Stream and implements already almost all its methods. At the end, a DataStream is just a virtual Stream that allows to read and write only segments of them and abstract for more generic types like MemoryMappedStream and LazyFileStream.

Also, other classes like DataReader, DataWriter, TextWriter and TextReader should work with the generic Stream. This way they will work with DataStream or any existing Stream.

Describe alternatives you've considered
None.

Additional context
This was needed to interact with some external compression libraries as well as xdelta-sharp. Requested also by @Kaplas80.