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/icore.h

@@ -119,7 +119,8 @@ public:
     virtual void addContextObject(IContext *context) = 0;
     virtual void removeContextObject(IContext *context) = 0;
 
-    virtual void openFiles(const QStringList &fileNames, bool switchMode) = 0;
+    enum OpenFilesFlags { None = 0, SwitchMode = 1, CanContainLineNumbers = 2};
+    virtual void openFiles(const QStringList &fileNames, OpenFilesFlags flags = None) = 0;
 
 signals:
     void coreAboutToOpen();