add support for validating yds content helper function

[capsulecorplab]

Helper function shall be allocated to "read" aspect of CRUD, along side load() function, as a linter for verifying expected yds content.

Note

This issue is an observation in response to ID behavior from #25

TODO's

• Shall include CLI applet for calling this function on yds data from the command line.
• Shall be used to lint test spec directories/data
• Helper function shall verify the following
  • data loads without error
  • metadata file exists when required (i.e, list contains complex data types and therefore expects a metadata file)
  • metadata file, when present, contain the expected properties
  • reports the presence of any extraneous files or directories
  • exit with a non-zero exit code if any of the aforementioned checks fail (for use in CLI applet)