Allow to pass all arguments/options to scaffold via command line

[anjensan]

Scaffold may be used by wrapper scripts or in some automation environment. Real use case: it may be integrated into script, which regenerates static project template (such script need to be reexecuted manually when new version of bigflow was released).

To do this 'start-project' (and presumably any scaffold-like commands) should expect to receive all parameters via cmd-line. Like:

bigflow start-project --non-interactive -Pproject_id='my_project' -Pgcp_bucket='some_gcp-bucket'

Alternative 1 - pass parameters via separate file (json, yaml?):

echo ...  > params.json
bigflow start-project --parameters-file params.json

Alternative 2 - provide custom cmd-line option for all parameters:

bigflow start-project --project-id "my-project" --gcp-bucket "..."

Alternative 2b - migrate to https://click.palletsprojects.com/en/7.x/options/#option-prompting #156