Make it easier to use annotation processing in Eclipse

[wilkinsona]

The Eclipse plugin applies an org.eclipse.jdt.core.prefs to a project that explicitly disables annotation processing. This makes it impossible to get annotation processing to work without manually tweaking the configuration each time the project has been imported/refreshed in Eclipse. We can hopefully just remove the configuration so that the Java Format plugin no longer expresses an opinion about whether or not annotation processing should be enabled.