CMakeProjectManager: Change editing cmake files to not pop up a dialog

Stop watching the cmake files for changes, instead watch the cbp file
for changes. Warn the user that changes in the CMakeLists.txt via a
infobar.

Fixes or obsolets a few bug reports:
Task-Nr: QTCREATORBUG-3123
Task-Nr: QTCREATORBUG-3353
Task-Nr: QTCREATORBUG-2487

src/plugins/cmakeprojectmanager/cmakeeditor.h

@@ -53,6 +53,7 @@ class CMakeManager;
 
 class CMakeEditor : public TextEditor::BaseTextEditor
 {
+    Q_OBJECT
 public:
     CMakeEditor(CMakeEditorWidget *);
     Core::Context context() const;
@@ -61,6 +62,9 @@ public:
     Core::IEditor *duplicate(QWidget *parent);
     QString id() const;
     bool isTemporary() const { return false; }
+private slots:
+    void markAsChanged();
+    void build();
 private:
     const Core::Context m_context;
 };