This class represent single XML element. Contains element name, namespace, attributes and inner elements if any.
Instances of this class are mutable and not synchronized, so it is required to make sure that only single thread will work
on particular instance of the Element class.
Warning
Methods which name contains StaticStr require that passed parameters are static strings, which mean that strings needs be static or result of String::intern() method.
This requirement is a result of usage == instead of .eqauls() for comparison inside this methods which make this comparison faster.
