New GM Pipe Organ Instrument

A response to this post on the forum: http://musescore.org/en/node/27106
a simple GM Pipe organ has been added to
instruments.xml and the old Pipe Organ which controlled Aeolus has been
renamed to Aeolus Organ. This is part of the preparations required for
the removal of Aeolus should we fail to resolve issues with Fons
Adrianssen.
Merge pull request #1024 from ChurchOrganist/NewGM-PipeOrgan

New GM Pipe Organ Instrument