Define Exception base/implementation classes

[Abhilash-Chandran]

In order to clearly pass on the information from the API to the user, it is important to define the known Exceptions and Errors.
This needs to be defined as a set of abstract and concrete classes in order to be used across the API and tested.

TODO:

• Define a base Dapr exception class
• Derive a base Dapr HTTP and GRPC exception class for client implementations.

Note: The server api is not planned as of now. In future in might evolve into a separate package within this project if necessary.