experimental support of dashboard node generation

[HiroyasuNishiyama]

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

This PR adds experimental support of Node-RED dashboard node generation.
See README.md for details.

Checklist

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• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the mailing list/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[coveralls]

Coverage increased (+0.2%) to 73.487% when pulling 21ae0e7 on node-red-hitachi:widget-template into 504a4c0 on node-red:master.

[kazuhitoyokoi]

@HiroyasuNishiyama This description is for function node template. Please replace "function node" and URLs with node-red-dashboard template node's one.

[HiroyasuNishiyama]

@kazuhitoyokoi thank you for pointing it. fixed description in LICENSE.mustache file.

[kazuhitoyokoi]

@HiroyasuNishiyama
Thank you for this. I have another request. Could you update the help in command line as another pull request? I hope that it's same as README.md.
https://github.com/node-red/node-red-nodegen/blob/master/bin/node-red-nodegen.js#L41-L78