Support network installer?

[piroor]

On Firefox 18, the installer of Firefox itself will change to a network installer.
http://www.ghacks.net/2012/10/03/firefox-for-windows-gets-a-web-installer/
We have two choices:

• Use the network installer. We have to update fainstall.nsi for the new installer.
• Use old-style offline installer (if it is provided by Mozilla).