Sort the package list using numeric sorting rather than alphabetic sorting

[gasche]

On the current last report, 0install versions are listed in the following order:

• 2.10
• 2.11
• 2.6.2
• 2.8
• 2.9.1

This has tripped me several time; in this particular case I was wondering why "old and recent versions" would be broken under 4.01, while some versions in the middle would work; in fact only 2.6.2 and 2.8 build under 4.01, they are the oldest versions.