* Start work on context aware backends

* Start work on moving the database plugins to gRPC in order to pass context

* Add context to builtin database plugins

* use byte slice instead of string

* Context all the things

* Move proto messages to the dbplugin package

* Add a grpc mechanism for running backend plugins

* Serve the GRPC plugin

* Add backwards compatibility to the database plugins

* Remove backend plugin changes

* Remove backend plugin changes

* Cleanup the transport implementations

* If grpc connection is in an unexpected state restart the plugin

* Fix tests

* Fix tests

* Remove context from the request object, replace it with context.TODO

* Add a test to verify netRPC plugins still work

* Remove unused mapstructure call

* Code review fixes

* Code review fixes

* Code review fixes