Make rule context available to enumeration loaders

*Moved from https://issues.jboss.org/browse/JBRULES-3271*

Currently, only fact field names are passed into data enumeration loaders. Sometimes, the enumeration list might need to change based on details about the rule being edited, like rule metadata or package name, etc. The request is to make the Rule object (along with all of it's metadata) available to data enumeration loaders. Perhaps have loaders implement the following interface:

public interface EnumLoader

{ public List<String> loadEnum(Rule r, String... dependentFields); }

This will enable support for more contextual enum lists. Very helpful for folks trying to integrate the standalone rule editor into applications.