Add support for dockerfile template

[matipan]

Signed-off-by: Matias Pan matias.pan26@gmail.com

Description

This PR adds support for the dockerfile template. In order to enable support users have to set enable_dockerfile_lang to true, it is false by default.
In order for this to be implemented the following changes were introduced:

• Update git-tar's faas-cli version to 0.8.6
• Modify git-tar to check if there are dockerfile functions and if the feature is enabled or not

Fixes #421

How Has This Been Tested?

I tested this using my own ofc installation and deploying matipan/of-git-tar:dockerfileSupport. Test cases:

• If the feature is enabled and there is a dockerfile function: here you can see that the build and deploy was successful
• If the feature is disabled and there is a dockerfile function: here you can see that the build failed with the error message: detected a dockerfile function but feature is not enabled
• If the feature is enabled/disabled a function that it's not dockerfile can be successfully deployed: I validated this using the e2e test from this PR

How are existing users impacted? What migration steps/scripts do we need?

Users will not be impacted since the feature is disabled by default.

Checklist:

I have:

• updated the documentation and/or roadmap (if required)
• read the CONTRIBUTION guide
• signed-off my commits with git commit -s
• added unit tests

[alexellis]

LGTM

[alexellis]

@matipan please can you pull in / re-sync any files from OFC into orc-bootstrap which are required for these changes? Thank you 👍