DKTL_MODE and DKTL_PROJECT_DIRECTORY broken

[paul-m]

Describe the bug

In support of WCMS-9796, I tried to get dktl to run under ddev.

This was unsuccessful, until I discovered I could use DKTL_MODE=HOST to force dktl to not manage the Docker containers.

However, this also did not work, because the dktl shell script ignores DKTL_PROJECT_DIRECTORY in a few important places.

Steps To Reproduce

Expected behavior

** Proposed Resolution **

Generally improve dktl so that it can run under vendor/bin/ in a project, and so that it can switch to DKTL_MODE=HOST while honoring DKTL_PROJECT_DIRECTORY.

[paul-m]

PR: #337