Issue #17 Generics : Bounded wildcards

Added tests. A quick and dirty fix shows that serialization almost works. But there is still compilation/cast problem with deserialization...
Issue #17 Generics : Bounded wildcards

Use the base type to find serializer/deserializer when the type is a JWildcardType.
Replace compile-time checks on HasSerializer and HasDeserializer by a cast. There was compiler errors when trying to return ListJsonDeserializer<Bean> to a method expecting JsonDeserializer<? extends Bean>