Fixing some of our XSLT implementation issues.

These changes move our XSLT code to passing 1898/3173 of the OASIS tests.
To contrast, the RI passes 2105/3173 tests.

Highlights:
  - Implementing getTextContent() for nodes
  - Removing validation during transforms. We don't support validation!
  - Fixing attribute constraints to match the spec
  - Fixing test suite to not confuse BaseURI from NamespaceURI
7 files changed