* removed tests from navigation iterators in PyXOM
* changed _python3 to _python2
* added deep copying for PyXOM, not tested
* added copying and manipulation with doctests to PyXOM
* changed attributes implementation in PyXOM, added more doctests, some bugs fixed
* added XML well-formedness checking to PyXOM
* added module "ecoxipy._helpers" containing XML well-formedness enforcers