Update libmei version support

Updated libmei support from MEI 2012 to 2013. Also, updated the libmei version from 2012.0 to 2013.0
Update Schema Parsing script

This commit removes support for roma-generated builds. Rather, all new schema parsing should be done with a compiled ODD. This was done because a) installing Roma is a pain, and b) it's quite easy to generate a compiled ODD of the latest version at custom.music-encoding.org.

Also, this commit changes the schema parser so that it creates separate sub-directories in the output directory for each language generated.
Update Python modules to latest version of MEI schema
Update C++ source and header files to new MEI version