Change Aeolus default to Equal Temperament

The default Aeolus temperament was Mean Tone which sounds out of tune to
our modern ears. I have changed the default to 5 (Equal Temperament) and
added information on how to change this at the head of the file.
Merge remote-tracking branch 'origin/master' into AeolusUpdate
Merge pull request #359 from ChurchOrganist/AeolusUpdate

Change Aeolus default to Equal Temperament