Add backing tracks for all basic exercises

Must Haves:
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II-V-I in 2 bars (Dm7, G7, CMaj7)
II-V-I in 4 bars (Dm7, G7, CMaj7)
Autumn Leaves
Minor blues (4x I, 2x IV, 2x I, V, IV, I, V)
Major blues (4x I, 2x IV, 2x I, V, IV, I, V)

Nice to have
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Chromatic minor 9 up - 12 chords - 48 bars (Band in a Box file already exists)
Whole tone starting at C - minor 7 up - 48 bars (Band in a Box file already exists)

It would also be nice to have some standards (not all translations needed) ->
Bye bye blackbird
All of me
Watermelon man
Cantaloupe Island

Specs:
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Prio is "Must Have" first.
Filename convention can be copied from the folder 'DONE - Minor7 chords - Funk - 1 chord/100bpm'


As you can see I already created the needed folders.
Keys: _C, Cis, D, Ees, E, F, Fis, G, Aes, A, Bes, B_

Note
Folders with WIP in the name are Work In Progress
Folders with DONE are ready for import in the iMproviser

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This ticket is done when we have:
- [ ] an .SGU for all "must have" backing track ins in all keys (swing 80pm and 100bpm, straight 120 bpm and 140bpm)
- [ ] a correct chord_info.txt in the root folder for the backingtrack
- [ ] a nice RealTrack based style in each 'bpm' folder