Overhaul of gen_robot_valid.py
Overhaul of gen_robot_valid.py

- Change from "Rvalid" to "Valid" name prefix.  Defined an rvalid_value
  alias to preserve backward compatibility.

- The validation functions' approach has been standardized so that all
  of the functions look quite similar to each other except for the
  function name and the corresponding name of the gen_valid support
  function being called.

- Docstrings have been standardized with several goals in mind:
  - Making them easier to maintain in this program.
  - Making them more palatable for use by robot's libdoc function.

- Since all of the validation functions' docstrings share a lot of
  common text, the docstrings are manipulated after the function
  have been defined.  Namely, each one has a standard header pre-pended
  to it.

- Added wrappers for gen_valid functions that were previously lacking:
  valid_type()
  valid_dir_path()
  valid_file_path()
  valid_path()
  valid_list()
  valid_dict()

Change-Id: I9c1b6822887d12a347a391e6b8f6086c581131af
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation