Lando should be able to install itself

[AaronFeledy]

Lando should be able to download and install its own dependencies and register itself in $PATH. This would allow a user to download the lando binary and run it as is, or "install" it without the need for an installer package.

• Create a Windows PowerShell script that handles requirements check, download/install of Docker, registration in $PATH
• Create Bash script that handles requirements check, download/install of Docker, registration in $PATH
• Add a lando command that downloads and runs the appropriate setup script