install.ps1: Fix persisting bug with already existing folder (#2732)
install.ps1: Fix persisting bug with already existing folder (#2732)

closes https://github.com/lukesampson/scoop-extras/issues/1300
closes https://github.com/lukesampson/scoop-extras/issues/1370
closes #2724
closes #2671
kodybrown/scoop,coonce/scoop,rasa/scoop,lukesampson/scoop,nikolasd/scoop,berwyn/scoop