midiCollection is restorable - no need to store it on Dropbox

[klesun]

• same applies for the heavy midiCollection_smf
• midiCollection_smf_bckp should be removed at all
• same applies to "a_opuses_json - Copy" probably
• the only important thing - some handwritten info, like scores, will lie in a db file in the git project root. it may go to git since it's tiny... likely

[klesun]

ok