Extremly flexible serialization interface for Java

Instead of extending <code>Appendable</code> make object instance of
<code>IAppendTo</code> and then it's possible to serialize it in to
existing Appendable implementations.

It is possible to extend this inteface to be parametrized by Buffer
interface and it should be considered in the future.
Simple pair container for Java

Useful in example when object has to return two values. Like in case when
returning only partially processed output.

Consider creating inteface for this object and also adding function that
provides iterator object.