#12 Made XMLDocument immutable
#22 StrictXML without external schema
#18 Unit test for validating with xsi:schemaLocation
Merge pull request #24 from carlosmiranda/12

#24: pull request #12 Made XMLDocument immutable
Merge pull request #25 from carlosmiranda/22

#25: pull request #22: StrictXML can now validate XML files without external XSD
#12 Made XML interface immutable
Merge pull request #26 from carlosmiranda/12

#12 Made XML interface immutable