Add a new kind of qualifier: key_set qualifiers

[JulienBortolussiAda]

Some qualifiers are actually expecting a list of value.

The current work around is to use key_value qualifier without choices and then to the parsing in the spec.

key_set qualifier will handle semi-column (";") separated list of values. The value will appears ordered in the build_space name.

[grouigrokon]

BTW, ";" is semi-colon. "," is comma :)