Removed unnecessary debugging code from mavgenerate.py
Added generation option to disable XML validation.
Useful when generating a lot of code and the XML files are known to be good, but it's still left on by default.
Extended support for disabling validation to the mavgenerate GUI.
Removed some redundant code from mavgenerate and made more code from mavgen reusable.
Merge branch 'master' of https://github.com/mavlink/mavlink into mavgen

Conflicts:
	mavgenerate.py
	pymavlink/generator/mavgen.py
Merge pull request #198 from Susurrus/mavgen

Added --no-validate option to mavgen.py