Label format:
List of channel names (and device types(Optional)).

EXAMPLE1 : Channel name list
Fp1
Fpz
Fp2
AF7
...

If device type is specified, positioning file(.pos.mat) for each device will be put.

EXAMPLE2 : Channel name + device type list

Fp1    EEG
Fpz    EEG
...

T1     NIRS
T2     NIRS
