Image version now accept a string of digit separated by dots and extra char as
a qualifier (~ or +).

Example:
1.2.3.4~dev < 1.2.3.4 < 1.2.3.4+dev

Old repositories are still compatible thanks to sqlite type affinity
(https://www.sqlite.org/faq.html#q3

).

We use a package version comparison algorithm for image version comparison
inspired by Debian.

Seblu: Fix typos

Signed-off-by: Sébastien Luttringer <sebastien.luttringer@smartjog.com>