Control mapping visibility from OSC (bug #43)

Controlled with /mapmap/mapping/visible mappingId visibility (type ii)
e.g.
oscsend localhost 7000 /mapmap/mapping/visible ii "3" "0"
to make mapping with id 3 invisible
oscsend localhost 7000 /mapmap/mapping/visible ii "0" "1"
to make mapping with id 3 visible

QListWidgetItem checkstate is also changed accordingly