Key Signatures - SCAMP - XML Exporting

[chnihy]

SCAMP does NOT currently support key signatures.
See the issue here. This is obviously a semi-big problem for the future of my app, and most likely means a different type of XML generation module will be required.

I've added an older version of xmlwriter.py to my github from an early mpm prototype. It uses LXML to custom print our MusicXMl files and will be integrated to replace
SCAMP in the next update.