Don`t ignore "nullable" for dynamic types

Currently the "nullable" property`s property ignored for dynamic type definition.

For example, the following code snip don`t work:
=====
DataObject dType = factory.create("commonj.sdo", "Type");
....
DataObject dProp = dType.createDataObject("property");
....
dProp.set("name", "XXXX");
dProp.set("nullable", Boolean.TRUE);
....
Type definedType = types.define(dType);
....
assertTrue(definedType.getProperty("XXXX").isNullable());

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