Merge topological_navigation and topological_map_manager packages.

Added the EstimateTravelTime service to provide a clean way of getting travel times of the topological map.
Added travel_time_estimator to standard launch file.
Moved Vertex and Edge into strands_navigation_msgs.

Basic test for travel_time_tester passes.
Added launch file for test, and test passing locally.
Removed topological_utils dependency.
Merge pull request #99 from hawesie/hydro-devel

Added travel time estimation service and refactored packages.