Support triggering GC for one project via REST

The Git garbage collection for one project can now be triggered by
POST on '/projects/*/gc'.

Change-Id: I6d45f33196f3f356648c817d9a2d8465de49bb5c
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-server/src/main/java/com/google/gerrit/server/project/Module.java

@@ -44,6 +44,7 @@ public class Module extends RestApiModule {
     put(PROJECT_KIND, "HEAD").to(SetHead.class);
 
     get(PROJECT_KIND, "statistics.git").to(GetStatistics.class);
+    post(PROJECT_KIND, "gc").to(GarbageCollect.class);
 
     child(PROJECT_KIND, "dashboards").to(DashboardsCollection.class);
     get(DASHBOARD_KIND).to(GetDashboard.class);