NCrystal release 0.9.8

• Decouple PhononDebye background cross-section code from .ncmat format, making it the new default also for .nxs files. For .nxs files, it is still possible to select the old behaviour of using curves provided by nxslib itself by configuring those files with "bkgd=external". A side benefit of this splitout can in some cases result in significant faster initialisation times when working with .ncmat files.
• Major cleanup and renaming of configuration variables, in preparation of the 1.0.0 release milestone. The renames are: mosaicity->mos, orientationprimary->dir1, orientationsecondary->dir2, orientationtolerance->dirtol, packingfactor->packfact, dcutoffupper->dcutoffup, scatterbkgdmodel->bkgd, scatterfactory->scatfactory, absorptionfactory->absnfactory and skippbragg becomes bragg but with opposite logic, e.g. bragg=0 disables Bragg diffraction. Removed entirely was the variables braggonly (use bkgd=none or bkgd=0 instead now) and nphonon. Experts can now instead tune parameters for specific background models by embedding them in the bkgd parameter value itself, e.g. bkgd=phonondebye:nphonon@20. As always, consult NCMatCfg.hh for a full description of parameters.
• Temporarily disable single-crystal speedup tricks while we investigate further, due to concerns that it is too aggresive (see github issue #13).