Consolidate file names

[musicEnfanthen]

This PR consolidates file names for the examples in v4. This mainly includes

• consolidation of author names, mainly Bach: Bach, Bach-J-C, JSB --> Bach-JS and Bach-JC
• uppercase spelling of titles
• uppercase spelling of opera: _Op5.mei
• unified use of No for parts of opera: _Op5_No1.mei
• enhanced use of opus numbers or work catalogue numbers (BWV, KV)
• inclusion of title or genre name if only opus number was given
• unified syntax for keys: G-major, c-minor
• fixing typos and different spellings of mei and pdf files