Enable Jinja2 templates from working dir

[roelschr]

Proposed changes

Enable users to (optionally) set the Jinja2 base working directory to os.curdir. By using the new option --jinja-working-dir, Jinja will treat the current directory as a working directory and Templates can be loaded from any namespace downstream.

This was the default behavior in version 0.6.0 but was removed at some point. Issue: #844

Types of changes

What types of changes does your code introduce to dbx?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

[RaviShivam]

.

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