api/services: move services into version directories

Signed-off-by: Stephen J Day <stephen.day@docker.com>

api/services/version/v1/version.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+
+package containerd.services.version.v1;
+
+import "google/protobuf/empty.proto";
+import "gogoproto/gogo.proto";
+
+service Version {
+	rpc Version(google.protobuf.Empty) returns (VersionResponse);
+}
+
+message VersionResponse {
+	string version = 1;
+	string revision = 2;
+}