UnresolvedType: fix JVM signature conversion

UnresolvedType: fix JVM signature conversion

Fixes #211. Previously, '?' was not converted to '*' in
UnresolvedType.nameToSignature, but kept as-is. That is why - falsely -
it was necessary to handle the '?' case in UnresolvedType.forSignature
at all, reading this kind of bogus signature and creating a type for it
in TypeFactory.createTypeFromSignature. This, ironically, led to correct
JVM generic type signatures containing '*' not being handled at all.

The conversion should now work correctly both ways.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>