TextEditor: Add delete(Start/End)OfLine actions

Task-number: QTCREATORBUG-18095
Change-Id: I75e6141687ba5e96ef59384b302357700f79dd55
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/texteditor/texteditor.h

@@ -359,8 +359,10 @@ public:
     void duplicateSelection();
     void duplicateSelectionAndComment();
     void deleteLine();
+    void deleteEndOfLine();
     void deleteEndOfWord();
     void deleteEndOfWordCamelCase();
+    void deleteStartOfLine();
     void deleteStartOfWord();
     void deleteStartOfWordCamelCase();
     void unfoldAll();