[FEATURE] Service generator added.

Scaffolder for the service added.
  $ hexx service AddItem -a code:required name -n success:item:messages error:messages

== Addons

* Hexx::Generators::Service.
* Hexx::Generators::Service::Attribute
* Hexx::Generators::Service::Notification

== Changes

* Hexx::Generators::Base added
* Hexx::Generators::Model is inherited from Base