EditorManager: add a flag for embedded linenumbers

And make use of it to accept on the command line the patterns:
"filename" "+45", "filename" ":23", "filename:12" and "filename+42"

Task-Nr: QTCREATORBUG-2428

src/plugins/coreplugin/coreimpl.h

@@ -88,7 +88,7 @@ public:
     void addContextObject(IContext *context);
     void removeContextObject(IContext *context);
 
-    void openFiles(const QStringList &fileNames, bool switchMode);
+    void openFiles(const QStringList &fileNames, ICore::OpenFilesFlags flags);
 
     void emitNewItemsDialogRequested();