Fix/union

[Kaiser1989]

Ok what we got so far:

We need to differ two deserialization strategies:

The manuel one:

NilUnionType b = mapper.readValue(new StringReader(out.toString()), NilUnionType.class);

here we need the getNullValue implementation of StdDeserializer

and the one used in Jackson Deserialization with JsonNode:

NilUnionType b = mapper.treeToValue(node, NilUnionType.class);

here we need the if (node.isNull()) check

I left both in there so we can't get something wrong then (one does not work without the other).

The other thing really was a bug when calling the constructor with null value, as constructor thought we put in a Integer or Boolean or String...

Which leads us to the next point: ambiguity!
I removed all constructors and only left one private empty constructor, indicating that the object was not correctly initialized (all null, also enum null)
And i added one constructor with Object as argument, checking the given value against all possibilities to build the correct Union type. This also handles the null value correctly and someone can use following code to create a StringNilUnion:

String test = ("sometext" or null);
new StringNilUnionImpl(test);

One does not need to care to call the empty constructor for null values anymore. If the type does not fit, an IllegalArgumentException is thrown.

Some other changes:

• Code cleanup
• Added helper function for Amibiguous testing
• Added helper function for type sorting
• One more test for a more complicated union of primitives
• Removed Creation of ObjectMapper for every conversion (use the one of context if no changes are made to the mapper => better performance)
• Fixed all warning by adding serialVersionUID
• Fixed map iteration in ExcludingMap (using entrySet iteration not key iteration)

[jpbelang]

I've quickly read through it, and will be giving it a real checkout tonight. This should get merged.