Minor text changes and a new screenshot

I tried to simplify and rearrange things a bit and corrected an error
or two
Moving source code download option

So it’s grouped together with the other download options and not
uninstall
New system icons

Updated windows logo
New icon for “From source”
New icon for “Uninstall”
Merge pull request #39 from andreaslarsen/master

Minor text changes and a new screenshot