V3 plot made compatible with latest data format, conductance comparison default set to qpc a1

Additional information on the data files

Only square lattices are implemented (automised) right now, the hopping parameter for rectangular lattices can be implemented easily (see report). It all depends on the definition of the Hamiltonian in the kwant system.

Functions needed to be adapted to be able to handle the new location of the data files folder. Now it is possible to specify the path towards this folder in qpc_exp2sim/qpc_exp2sim/tools/data_handling.py on line 17.