Accessor for the temporary workspace/selected project.
New method DXJSON.safeTreeToValue (wraps ObjectMapper.treeToValue).

Update some DX classes so they no longer throw JsonProcessingException.
Add and reformat docs for DXContainer, DXProject, DXObject.
PTFM-7307: Basic support for job tags and properties

Add support in:
- dxpy.DXExecutable.run
- dxpy.DXJob.new, dxpy.new_dxjob
- dxpy.find_jobs
- dx describe
- dx run with --tag, --property (BREAKING change; removing --tag from
  being equivalent to --alias/--version for specifying a version of an
  app to run)
- dx find jobs with --tag, --property

Also reorder some kwargs to group metadata args together