Simplify and generalize project imports in P2's Oomph setup

The root .project file of p2 is removed via
eclipse-equinox/p2#149

The abandoned project 'org.eclipse.equinox.p2.testserver' has been
deleted as part of eclipse-equinox/p2#49

releng/org.eclipse.equinox.releng/Equinox.setup

@@ -269,15 +269,7 @@
         <requirement
             name="*"/>
         <sourceLocator
-            rootFolder="${github.clone.equinox.p2.location/bundles}">
-          <excludedPath>bundles/org.eclipse.equinox.p2.testserver</excludedPath>
-        </sourceLocator>
-        <sourceLocator
-            rootFolder="${github.clone.equinox.p2.location/examples}"/>
-        <sourceLocator
-            rootFolder="${github.clone.equinox.p2.location/features}"/>
-        <sourceLocator
-            rootFolder="${github.clone.equinox.p2.location/org.eclipse.equinox.p2.releng}"/>
+            rootFolder="${github.clone.equinox.p2.location}"/>
       </targlet>
     </setupTask>
     <setupTask