Per-Machine installs

[anaisbetts]

This PR adds a new --machine parameter that will install the app for all users (they may need to log out and log back in)

TODO:

• Verify this works correctly to install on the current profile
• Verify this installs on a current user that isn't the current profile
• Verify this installs on a newly created user
• Uninstall detritus gets detected as valid install
• Silent doesn't get passed to Update.exe
• Installing as admin should install for admin's profile

Fixes #314

[Neustradamus]

All good softwares when we install use by default "Program Files" (or recently "Program Files (x86)" for 32 bit apps in 64 bit system).
Bad softwares do not use it.

It is since Windows 95 and maybe before, no?