Updated the two_step_routing library.

New features and changes:
- added support for TransitionAttributes in the models.
  TransitionAttributes are now preserved from the original scenario, and
  parking location tags can now be used as srcTag or dstTag in the
  transition attribute specification.
- in the local model, allow grouping shipments only by parking location
  instead of grouping by a parking location and time. This new option
  creates more compact local routes, but it may lead to increased
  skipped shipments.
- added an option to reuse existing results for local and global model
  solutions, if the corresponding files exist.
- allow using the "internal parameters" string in the original request.
- preserve the road traffic setting from the original request (in the
  global model only).
- modified all datetime code to work with datatimes with time zone info.
- added functions for analyzing and transforming scenarios and
  solutions.