Create abstract type inheritance class

[i0bs]

Proposing us to add some form of an abstract class that expects a Id prop of Guid. The motive behind this is that having a separate class means we could provide helper methods for handling things with the base object and ID.

For regular .NET usage, users can inherit it if they wish to tap in for more helper methods and robustness.

For code generation, I propose we inherit it by default for ease of use.