Validate further XML files

Do simple XML validation of .xsd, .xsl, .xjb files - just for well-formed XML,
no schema validation yet.

Fix a bug introduced with version 0.2 that we did not use a schema
for .wadl files. Testing this, there were too many errors with the RelaxNG
validation, so use XMLSchema as recommend by David Cramer.

Added XMLSchema files for local parsing.

Change-Id: I589f00a2e3dc46b6b3ba5e965fa9d4eba6d1a295
Merge "Validate further XML files"