include remote-repo URIs for offline installations in /etc/apt/sources.list

[Elmar Stellnberger <estellnb@gmail.com>]

  The remote-repo URIs should always get included into /etc/apt/sources.list 
on installation. It is possible that we install in a place without internet 
access and want to connect our computer later. Some security hints also 
suggest to always install offline and shut all services down before connecting 
the first time. Moreover we still have computers being offline most or all of the 
time.
  My suggestion simply is to put all remote repo URIs into 
/etc/apt/sources.list in any way also if the installation is proceeded offline.
If we select offline or abort a connection attempt these lines should simply
be commented out rather than fully deleted. We will also need them for 
computers kept 100% of the time offline since we can transport software 
to them via a USB disk or stick taking our sources.list and 
/var/lib/dpkg/status with us to feed apt with the necessary information for an 
offline installation.

Best Regards,
Elmar Stellnberger