Adds more keywords to the OSGi declarative service preference page

Adds OSGi and declarative service to the key words for the preference
page to make it easier to find this setting.

ds/org.eclipse.pde.ds.annotations/OSGI-INF/l10n/bundle.properties

@@ -13,7 +13,7 @@
 ###############################################################################
 Bundle-Vendor = Eclipse.org
 Bundle-Name = Declarative Services Annotations Support
-keyword.label = ds
+keyword.label = ds, OSGi, declarative service
 property.page.name = DS Annotations
 preference.page.name = DS Annotations
 problem.marker.name = DS Annotation Problem