Support cycle mode

[Benjamin Klum]

Right now, Playtime automatically switches off cycle mode because it interferes with its looping logic. But that's too strict. There might be a way to support cycle mode, of course with restrictions because naturally these two approaches of looping don't fit.

[Benjamin Klum]

Resolve #40 Don't switch off REAPER repeat mode when just playing, only when recording

→ <<cset fe7e20cec7a3>>

[Benjamin Klum]

Please note: There's no improvement in the looping logic itself. Playtime cannot play a continuous loop within a REAPER time selection right now if the time selection is not exactly a multiple of the clip length. This is requested in issue #50, a different issue.