feat: DiffractionObject.load() method

[sbillinge]

Problem

We can dump easily but we can't yet load

Proposed solution

define a DiffractionObject.load() method that uses loadData but just loads it into a diffraction object with all the header info in metadata

my_do = DiffractionObject().load('path/to/file.chi')

gives a valid DO. It could look for wavelength and xtype in hte header, but if can't find it it needs to throw an error or a warning and ask to rerun specifying, for example

my_do = DiffractionObject(wavelength=1.54,xtype=q).load('path/to/file.chi')