Prefer the usage of OSGi ds services instead of the CorePlugin service registration

[vogella]

In #1148 a deadlock was identified and I looked into the org.eclipse.buildship.core.internal.CorePlugin which registers tons of OSGi services in its start method. You should move these to OSGi DS services.

For this:

1.) Activate the DS Preferences via Windows -> Preferences -> Plug-in Development -> Ds Annotations

2.) This allows you to use the @Component annotation to define OSGi immediate components or OSGi services. The 1.) ensure that the IDE generates the corresponding meta-data for these services.

cc @laeubi and @HannesWell as they are working on this in platform and might be interested in helping buildship to update.

[laeubi]

If you have questions let me know but I doubt I won't be able to help here as I'm not using gradle at all...