A2.5: default lookup

Default look will be based only on META-INF lookup. The content of current /Services folder from SystemFS will be removed from default lookup. Instead of that clients should use Registry API to access directly the context with their instances and process them as they need.

Random thoughts:

There already exists lot of subfolders below Services folder for concrete types of services. This pattern should be recommended for all new kinds of services.

This change will be incompatible. Anybody using default lookup to find for example instance of CompilerType will after this change found nothing. One possible solution for backward compatibility could be to hardcode all well-known types into default lookup and when somebody is searching for that type the warning could be logged, but new place with instances of that type could be search for some instance. Eg. searching for CompilerType logs warning, but checks /Services/CompilerType context for some instance. What is it "some" needs to be clarified. This would solve backward compatibility in lot of cases, but definitely not in all. All contracts defined outside of OpenIDE would be broken.

Instances required to be in default lookup will have to be registered in META-INF folder.

Some instances like SystemOptions should be killed from /Services folder at all.