move benchmark_* files to benchmarks/ from /scenarios. Update docs and scripts

Depends on

• https://github.com/wavelab/anm_sim_platform/pull/17

Testing:

1. $ rosrun anm_sim_platform benchmark.py should run default benchmark.scenarios and produce benchmark.results the same as benchmark.expected.
2. rosrun anm_sim_platform benchmark.py _name:=aaa should run aaa.scenarios and produce aaa.results the same as aaa.expected.
3. rosrun anm_sim_platform benchmark.py _name:=bad_name should run bad_name.scenarios and produce bad_name.results the same as bad_name.expected. Result 7.

You can close the simulator and rosnode kill hdmap_server to get results 5 and 6.

You should never see results -1 and 4 in the .results files as they are internal to benchmark and transient.