Schematics: add schematics for reducer creators

[brandonroberts]

Follow up to #1480

1. Adds an reducerCreators option to the reducer, feature, entity schematics that uses the new reducer creator functions instead of switch case
2. The reducerCreators flag will use a different set of files for scaffolding. This keeps our current structure with files intact.
3. Adds tests to verify the behavior of the previously mentioned schematics
4. Also needs to handle registering a feature reducer with a generated reducer wrapped in an exported function