Updated ScreenShot name in menu

Updated the ScreenShot name in menu to point out that it is only of
skilled nodes, not the whole tree.
Update README.md

Added Install/Update instructions
Organizing of MainWindow.xaml.cs

Started cleaning up MainWindow.xaml.cs and moving things around to
better fit.
Update README.md
Finnished organizing MainWindow.xaml.cs

Organized methods into regions and some renaming.
More renamning
Fixed more conflicts
Conflicts:
	WPFSKillTree/Views/MainWindow.xaml
	WPFSKillTree/Views/MainWindow.xaml.cs