Features/navigation attributes

Please note this PR removed template from Navigation with the idea that it will become an attribute.  Please note https://github.com/interchange/Dancer-Plugin-Interchange6/issues/19

* Move logic from User profile into new Base::Attribute
* Added result classes NavigationAttributeValue, NavigationAttributeValue MANIFEST
* Added base class Base::Attribute
* Added test base_attribute.t to MANIFEST
* Additional improvements to input args for Base::Attribute methods