Updatet ui fixed bugs, improved performance, just everything

Autors:
@DerAnonymos
@AshBastian
@Sonaion

src/Tool/IntelliTool.h

@@ -25,8 +25,9 @@ enum class Tooltype {
 private:
 /*!
  * \brief A function that creates a layer to draw on.
+ * \return Returns if a layer could be created
  */
-void createToolLayer();
+bool createToolLayer();
 
 /*!
  * \brief A function that merges the drawing- and the active- layer.