request: add an `instance` property to base

[jonschlinkert]

I think we can clean up the root of the the base object by moving any "internal"/private properties to the instance object.

For example, we can move base.alias, base.namespace, base.name etc.

if (base.instance.namespace === 'generate.foo.bar.baz') return;
if (base.instance.name === 'generate-baz') return;
if (base.instance.alias === 'baz') return;

This would keep the object cleaner