Identifier descriptions (#20)

* Add optional description field for NamedEntityIdentifier

Adding endpoints for metadata, updating dependencies

Updating protoc image

Changing metadata update request to parse the body into the metadata field

Moving metadata out of NamedEntityIdentifier and using composition instead

Re-thinking how named entities work

* Fixing generation

flyteidl/Makefile

@@ -9,7 +9,7 @@ update_boilerplate:
 
 .PHONY: generate
 generate: # generate protos, mocks and pflags
-	dep ensure --vendor-only
+	dep ensure -vendor-only
 	./generate_protos.sh
 	./generate_mocks.sh
 	go generate ./...
@@ -19,7 +19,7 @@ test: # ensures generate_protos script has been run
 	make install
 	git diff
 	go get github.com/lyft/flytestdlib/cli/pflags
-	dep ensure --vendor-only
+	dep ensure -vendor-only
 	./generate_mocks.sh
 	go generate ./...
 	DELTA_CHECK=true ./generate_protos.sh