Refs #6007 - fixing safe_value for lookup key

Fixes #12806 - adding merge_default to attr_accessible in lookup_key

Fixes #12180 - lookup_value presence validation moved from lookup_key

Global parameters can have empty values so smart variables that are also global should be allowed to accept empty values too.
The validation on lookup_value to make sure it isn't empty is in the LookupKey class therefore affecting both VariableLookupKey and PuppetClassLookupKey....

fixes #11862 - validating that casted hash is valid

Catch parse errors correctly under Ruby 1.9.3, and ensure the uncasted
value is displayed back in the UI if it fails to parse.

Fixes #6007 - Allowing to hide smart class parameters

Fixes #7568 - Use attr_accessible for Rails 4 upgrade

Fixes #11458 - Override inline for class parameters

This implements override inline for smart class parameters and smart
variables in host and hostgroup edit forms.
Global variable override inline will be done in a seperate PR.

Authors:
Ori Rabin <orrabin@redhat.com>...

fixes #12095 - prevent escaping of lookup key default value with ERB

When the current default value is retrieved from a lookup key via
default_value_before_type_cast, do not re-dump values containing ERB as
they will not have been cast already. This prevents them being escaped...

fixes #11964 - mark existing parameters as overridden during clone

Fixes #11851 - include ActiveRecord::Base.inherited as super in LookupKey.inherited