Augment "dx find data --path" to receive as input a relative path from current working directory or a path in "project_id:folder_path" format.

Summary:
Existing "dx find data --folder" functionality transferred to "dx find data --path"; --folder flag will be deprecated.
Additionally deprecated --project flag for "dx find data"; project can instead be optionally specified as input to --path flag.

Test Plan: Regression and unit tests (test_dx_find_data_by_scope).

Reviewers: psung

Reviewed By: psung

Differential Revision: https://phabricator.dnanexus.com/D121