Add support for dev hub based on the project

[jefersonchaves]

Is your feature request related to a problem?
It is a feature. Consultants and other service providers that work with multiple customers need to switch between dev hubs.

What are you trying to do
Would like to have multiple projects and have the default dev hub saved inside the project similar to default scratch org.

Describe the solution you'd like
Store the dev hub on project file along to default scratch org.

[aheber]

@jefersonchaves isn't this already available?

While in a project you should be able to run sfdx force:config:set defaultdevhubusername=[devhub@project.com] and that should set the value in the .sfdx/sfdx-config.json and be scoped just to that specific project.

I just did that today so it should work...

[jefersonchaves]

@aheber: fantastic, that is exactly what I needed. I will play around that.

Now I found on force:config doc but I guess it can be improved.