Fixed potential offset bug, now version 2.3

Signed-off-by: christophys <christoph.koch@uni-ulm.de>
Update of Matlab GUI

Signed-off-by: christophys <christoph.koch@uni-ulm.de>
Merge branch 'master' of https://github.com/christophys/QSTEM into christophys-master

Conflicts:
	libs/fileio_fftw3.cpp
	stem3/stem3.cpp
	stem3/stemlib.cpp