Fixes#407 (partially) and #441
Description of the changes:
Remove TitleBarHelper and all <Border x:Name="CustomTitleBar" />
Let the system defines the draggable region
Centralize all events and functions associated to the title bar in a single control TitleBar instead of code splitted between MainPage/TitleBar/HistoryList/Memory.
Use the standard title bar when high contrast is activated instead of the custom one.
Modify the color of the title when the window doesn't have focus
Fix the right padding of the title bar with high contrast
How changes were validated:
Manually tested with LtR and RtL languages
Manually tested with high contrast
Tested when History and Memory flyout are opened
If we allow users to select texts, the application will feel more like a "Desktop app", will be easier to use on a tablet and users will be more prompt to use Ctrl+C to use the result in another app.
