Search SDK: Updating Management SDK surface area, part 1

This is part 1 of a final pass over the Swagger spec for arm-search. Types of
issues that are addressed include:

  - Consistency of parameter names (serviceName -> searchServiceName).
  - Consistency of method names with established Azure conventions
    (List -> ListByResourceGroup, etc.).
  - Added the ability to pass in x-ms-client-request-id (test coverage still
    pending).
  - Correctly modeled error cases for all key management operations.
  - Enabled paging for List operations (although the Search RP doesn't support
    paging, we at least benefit from the improved client programming model).

Part 2 will address the same sorts of issues in Search service management
operations.