PTFM-13152 Remove app-specific validations when building applets.

Summary:
Additionally check for existence of applet with same name in
destination before uploading resources when "dx build" not
supplied with "-f" or "-a" flag and add tests for building applets.

Remove do_build_step and do_upload_step from build_and_upload_locally() declaration.

Add lint fixes and minor changes.

Test Plan: ./test_dxclient.py TestDXBuildApp

Reviewers: psung

Reviewed By: psung

Subscribers: psung

Differential Revision: https://phabricator.dnanexus.com/D149
Bash vars bugfix and style improvements
Changelog and version updates for v0.124.0, UA 1.5.5
PTFM-13730: expanding the bash path variable

Summary: Expanding the bash path variable, and uplifting the tests accordingly.

Test Plan: Improved the file_load/vars test.

Reviewers: klai

Reviewed By: klai

Differential Revision: https://phabricator.dnanexus.com/D155
Bump concurrent.futures dependency from v2.1.2 to v2.2.0

Also rewrite the monkey-patch for threadpool executor that
incorporates the fix for http://bugs.python.org/issue16284.
Bump requests dependency from v2.3.0 to v2.4.3
Changelog and version updates for v0.125.0
Fix instability in dx-toolkit file/deepdirs test

Summary:
Adding a wait-for-close flag, when uploading a file. This is part of the dx-upload-all-outputs
script.

Test Plan: Existing tests, especially file/deepdirs.

Reviewers: klai

Reviewed By: klai

Subscribers: bagee

Differential Revision: https://phabricator.dnanexus.com/D160
Merging versions