Only prevent sleep if we are printing
Preventing sleep was happening whenever the print window was open
but it should prevent sleep only if we are printing.
If we close the print window though, it will re-enable sleep capabilities
because we wouldn't be able to know when the print has finished anymore
Prevent forced sleep on windows by going to away mode when supported
This will prevent the computer from going to sleep even if the user
puts the computer to sleep manually. It will go to awaymode
which is identical to sleep mode but the application will keep running
in the background until it is done.
This should help with issue #46