McaTheory.setData limits priority: function arguments > configuration > full range

[woutdenolf]

Restore the intended behavior of the xmin and xmax arguments of McaTheory.setData which was changed in c713a49.

The final xmin and xmax values are defined with this order of priority

1. If the xmin or xmax function argument is not None: take it.
2. If use_limits=True and the "xmin" or "xmax" value from the configuration is not None: take it.
3. If the xdata is not empty: take the min(xdata) or max(xdata) value.
4. xmin=None or xmax=None (not needed anyway).

[vasole]

Please, review my contributions too!

[woutdenolf]

LGTM for me.