Add definitions for new api error type

[manoranjith]

Description

• The newly added error type will facilitate easier handling of error scenarios by the user of api over remote interface.

• Each error will include

  • Error Category: A numeric code describes how error should be handled.
  • Error Code: A numeric code that describes specific error conditions. Unspecific errors are assigned code corresponding to "internal unknown error".
  • Message: Actual error message.
  • Additional Info: Contains additional data for handling the error as key value pairs.

• Each of the methods in node, session and channel API will be updated to return errors of the newly defined type in upcoming pull requests.

• Proto file have also been updated to include the same definitions.

Category

Implementation Task

Relevant issue

Relates to #132.

Testing

Steps to run the tests

1. Test_ErrorCategory and Test_ErrorCode have be included in api/grpc package to test the mapping from error constants in the project to those in the grpc adapter.

Checklist

• [x] Name is added to the NOTICE file, if it is not present already.
• [x] Changes are rebased onto the target branch.