Create helm lint command

[sgoings]

In order to help people create new charts and maintain a high standard of quality within the charts repo, I'd like to see a lint command within helm. The exact specifics of what "linting" mean are up for discussion but at this point @gabrtv and I have discussed:

• is the Chartfile well formed?
• are the manifests well-formed?
• do the Docker images exist?
• is the heritage of the Docker images trusted?
• do the dependencies exist, and are the version constraints possible to match?

helm lint would then be run on charts that are submitted via PRs.

[technosophos]

And "are the manifests well-formed"

[technosophos]

"Do the dependencies exist, and are the version constraints possible to match?"

[michelleN]

+1

[sgoings]

Added both of @technosophos suggestions.

[michelleN]

Some of the criteria in this issue have been moved to helm/helm#300