Added base TransportAction class for master read operations that execute locally or not depending on the request class (local flag).
Added support for local flag where missing, in a backwards compatible manner:
- IndicesExistsRequest
- GetAliasesRequest (get alias api, aliases exist api)
- TypesExistsRequest
- GetIndexTemplatesRequest (get template, template exists)
- GetSettingsRequest
- GetRepositoriesRequest
- PendingClusterTasks
Added parsing of the local flag where missing in Rest*Action.
Updated SPEC adding local flag param where missing and added REST tests that contain use of the local flag where it was just added.
Closes#3345