Imports of updatetree command

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
errorsPackage errors implements functions to manipulate errors.
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/golang/glogPackage glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup.
github.com/golang/protobuf/protoPackage proto provides functionality for handling protocol buffer messages.
github.com/google/trillianPackage trillian contains the generated protobuf code for the Trillian API.
google.golang.org/genproto/protobuf/field_maskPackage field_mask aliases all exported identifiers in package "google.golang.org/protobuf/types/known/fieldmaskpb".
google.golang.org/grpcPackage grpc implements an RPC system called gRPC.
google.golang.org/grpc/codesPackage codes defines the canonical error codes used by gRPC.
google.golang.org/grpc/statusPackage status implements errors returned by gRPC.
timePackage time provides functionality for measuring and displaying time.