New feature in conversion, and for user set

[techAdmin]

During conversion process, now all users are asked to set their default upgrade type, dist-upgrade or upgrade.

For most users of testing and sid based systems, they would want to use dist-upgrade, but they will now get the choice.

Non antix conversion users will also get to pick between using aptitude and apt-get in smxi.

This covers the basics of smxi being more truly debian compatible.