Added more characters to Mark Short Label

Hi,

I'm a huge fan/user of AnyTune Pro+. I use it pretty much every day.

I use Marks to enter chord changes in charts that I am working on. It would be REALLY GREAT to have more than 2 characters for the flags on the timeline eg, F#m7, F#°7 etc. 4 characters would definitely help.

Thanks for the great app.

Best,

Jim