Added geodesic distance for multiple goals

.circleci/config.yml

habitat/core/simulator.py

habitat/datasets/pointnav/pointnav_generator.py

habitat/sims/habitat_simulator/habitat_simulator.py

habitat/tasks/nav/shortest_path_follower.py

habitat_baselines/common/environments.py

test/test_habitat_env.py

test/test_habitat_sim.py

test/test_mp3d_eqa.py