histogram ... support for breaks

[RLumSK]

In its current version, the app histogramdoes not support a manual or semi-automatic (with keywords) setting of breaks. However, the user should be able to adjust the breaks (bin width) of the histogram using the at least a few of the options provided by graphics::hist.

Implementation note: The function Luminescence::plot_Histrogram does not treat the argument breaks as expected (cf. R-Lum/Luminescence#54)