Added travel time estimation service and refactored packages.

This PR merges topological_map_manager into topological_navigation and moves the Edge and Vertex messages from topological_utils to strands_navigation_msgs.

This also adds a service to estimate travel time between two nodes. This is necessary to support the scheduler before the MDP planning bits are released. At which time we can use that instead of the simple node I added. This can be tested with `catkin_make run_tests_topological_navigation`.