Add a boilerplate data source

[zackkatz]

Also based on a call with Mark. He said it would have been helpful to provide a boilerplate as a starting point.

I'm not sure exactly where this would be in the code structure…Perhaps another repo altogether?

[doekenorg]

@zackkatz We could ship the SDK with an executable that can scaffold a data source, field, future things (like custom layout?).

Something like:

vendor/bin/datakit make:datasource "My\Namespace\YamlDataSource" --extend-base --is-mutable

Or have it ask questions like:

• What is the FQCN of your class
• Do you want to extend the base class (answering "no" would create a class that implements DataSource instead
• etc

It would create the file from a predefined scaffold file with placeholders.