Add label support

[alexellis]

Signed-off-by: Alex Ellis alexellis2@gmail.com

Description

Adds label support for functions

Motivation and Context

Needed for openfaas/faas#325

How Has This Been Tested?

Tested with openfaas/faas#325 - via:

• YAML
• YAML plus arguments --label
• Via arguments only --label

This change has a back-end fix with swarm, but Kubernetes support will come in a follow-up PR.

Types of changes

• Bug fix (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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.