BUG-1276: fixed generated union constructor

Current generated definition of union constructor

public UnionType(Arg1 _arg1) {
  super();
  this._arg1 = _arg1;
  this._arg2 = null;
  this._value = null;
}

was incorrect and setting this._value == null was replaced with setting _value to correct value, for example:

this._value = arg1.getValue()
or
this._value = _arg1.getValue().toString().toCharArray()

Change-Id: I837e5e1fc6845937d19abcdc8e2f8d52b410d316
Signed-off-by: Martin Vitez <mvitez@cisco.com>
Merge "BUG-1276: fixed generated union constructor"