Sketchinn drawings still shown in screenshot. about watchntouch HOT 4 OPEN

This is due to the way sketching is currently implemented, it's done via 
AnnotationWidget which has context recall and thus reloads the last drawings. 
To fix this, we need to move sketching to its own widget (SketchingWidget, 
derived from BaseDrawingWidget) and display this widget instead of 
AnnotationWidget when sketching is selected from the menu. This will require 
some UI refactoring for MainWindow so let's keep it like this for the moment.

r85, This problem has been fixed just fixing a little bug in the program. 
SketchingWidget will be the upcoming step after discussing its necessity.

SketchinWidget decided to be integrated to the system as it is required by SDD. 
Working on it.

r86, sketching component has been constructed. Some basic changes and logics 
applied is the following

1 - A new object named SketchingWidget.cpp is created. This a new class derived 
from BaseDrawingClass. 

2 - A new QWidget variable named groupForSketching is created. This is to group 
the objects of SketchingWidget and the Qlabel that holds the pixels of blank 
image or screeshot

3 - Old variable named group(AnnotationWidget object) 's name changed as 
"groupForPresentation".

4 - A new variable named "stackWidget" is introduced. This is a QStackedWidget 
object and keeps two widgets groupForPresentation and groupForSketching. As 
stack provide us having one of the widget is active at the same time, these 
widgets are used alternatively by the lines

widgetStack->setCurrentIndex(ANNOTATION_WIDGET);
widgetStack->setCurrentIndex(SKETCHING_WIDGET);

in the required places.

5 - Due to the state diagram attached to the note, there are two 
sketchingwidget component. One is to keep sketched data one is to keep 
screenshot data. Indeed, It is only for "open existing sketch" option. We have 
to keep sketching's drawing data seperate from the screenshot drawingdata in 
order not to destroy sketching's drawing data when we load a screenshot image. 

Note that only one sketchingwidget is visible at a time.

6 - mainwindow constructor, openNewSketch(), openExistingSketch() and 
openScreenshot() functions can be examined for the changes.