Handle non generic subclasses of collections / Maps

[pauxus]

for example:

class TypeMap extends HashMap<String, MyType>...

@DSL
class User {
    TypeMap types // keytype String, elementTypeMyType
}

or even:

class SpecialTypeMap<T> extends HashMap<String, T>...

@DSL
class User {
   SpecialTypeMap<MyType> types // keytype String, elementTypeMyType
}

This should be implementable by improving getKeyType and getElementType methods

Might be somewhat related to #180