Core: simplify ILocator interface

Use data members instead of virtual functions for id, displayName and
priority, use Core::Id, not QStrings for id, de-pimpl CommandLocator.

Change-Id: Id8b41f184cb995138b2d76c923d6d3ae02b7e3f5
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/coreplugin/id.cpp

@@ -323,4 +323,9 @@ CORE_EXPORT const char *nameForId(int id)
     return stringFromId.value(id).str;
 }
 
+bool Id::alphabeticallyBefore(Id other) const
+{
+    return toString().compare(other.toString(), Qt::CaseInsensitive) < 0;
+}
+
 } // namespace Core