Add Text tool

closes #11
Add an initial version of the text tool.
This commit adds:
- Basic text tool.
- On demand thickness and color update.
- Generalized logic for future widget based tools.

src/core/controller.cpp

@@ -104,6 +104,7 @@ void Controller::startVisualCapture(const uint id, const QString &forcedSavePath
         } while (modalWidget);
 
         m_captureWindow = new CaptureWidget(id, forcedSavePath);
+        //m_captureWindow = new CaptureWidget(id, forcedSavePath, false); // debug
         connect(m_captureWindow, &CaptureWidget::captureFailed,
                 this, &Controller::captureFailed);
         connect(m_captureWindow, &CaptureWidget::captureTaken,