Reopen: Added missing path types

[videh25]

fix #341

Reopening the PR #892 since it was closed due to deletion of head repository.

Committed the same changes:

1. Added missing RS paths and refactored the code.
2. Modified assert condition in test3 of test_rrt_star_reeds_shepp.py.

Summarising the discussion from PR #892:

1. "x" in the function names refers to the direction switches.
2. Had to change the assert condition in test3 of test_rrt_star_reeds_shepp.py due to some strange behaviour. I have mentioned this in detail in this issue.

CheckList

• Did you add an unittest for your new example or defect fix?
• Did you add documents for your new example?
• All CIs are green? (You can check it after submitting)

[AtsushiSakai]

LGTM. Thank you!!