fix: New `PDFParser` cannot parse PDF data from the NOMAD pdf file

[cadenmyers13]

Problem

Pointed out by @benfrandsen

In earlier versions, the PDFParser could recognize the standard comments prepended to data files produced on the NOMAD instrument at SNS, such as:

# 5000
# file: PDF/NOM_9999_MnO_5K_ftfrgr.gr
# created: Thu Sep 29 18:48:08 2016
# Comment: neutron, Qmax=31.414, Qdamp=0.017659, Qbroad= 0.0191822
#

The parser would recognize that the scattering type is neutrons and automatically pull out values for Qmax, Qdamp, and Qbroad. In the current version, it does not automatically pull out any of this information, requiring the user to provide it.

Proposed solution

Add this parsing ability back