TODO:
background correction tool
- radio button Channel1 Channel2

Save session bg2correct
-> 0.8.1 version only, secure backwards compatibility

intensity read only on panel

when hitting apply, bg2 is changed

disable channel2 amplitude corrections in AC mode
(plot all)

background correction tool
enable all when AUTO bg is set

check bg correction formula
New background correction works in principle
BG correction integration into statistics and page info