Add function of Screen Shot.
Add context menu: Graph Style.
Add logic for graph style menu click.
Add context menu: Show Grid.
Add context menu: Screen Shot.
Merge branch 'feature/context-menu' into develop
Simplify the DrawVerticalGrid method.
Remove DisplayRect in class DataGraph.
Add new subClass.
Separate Get and Do method for DrawGrid.
Fix bug: Unable to drag in Y direction.
Refactor axis scales drawing.