Slayer generate scaffold

[ncallaway]

Generate the full scaffold for a command. This should generate a Command, and the Form for a command. It should also take type parameters that are used to generate the Form.

The validating the type of the Form should automatically be added at the top of the Command.

[wkirby]

forms/foo_form.rb
commands/foo_command.rb
spec/factories/forms/foo_forms.rb
spec/forms/foo_form_spec.rb
spec/commands/foo_command_spec.rb