see getUniProtID() in moltab.js

WE DON'T NEED TO GET PDB-ONLY "p" SEQUENCES. THEY ARE ALREADY AVAILABLE.
"PDB" DBREF lines ("p" below) are chains without UniProt sequences.
Could get from e.g. https://www.ebi.ac.uk/pdbe/entry/pdb/6um7/protein/4

dbref1 always followed by dbref2 are used when the database accession number won't fit
into the dbref slot. In such cases, the acc# is truncated (wrong) in SEQADV.
See seqadv.txt

jgetfi("dbref1") gets only the first instance. Jmol assumes all records with the same name will
be sequential. 

jgetfi("dbref") FAILS when dbref1/2 occur between dbref records, examples:
(Search method: get 6K PDB IDs from pdbRecNames for DBREF1.
Enter those at RCSB and # of distinct protein entities = 4)
 - 6KL4 6KL4 L S p
 - 2IY3 2iy3 S L (L=GB) p (p = PDB not UNP)
 - 5yl2 5YL2 6 protein chains, short/long IDs: S L S L S S. all UNP
 - 6BYP 6byp L L homodimer
 - 6UM7 6UM7 12 PROTEIN CHAINS: L S p p S L p p S p p L
 - 6VK5 6VK5 8 CHAINS L L L L L L L L (4 SEQUENCE DISTINCT)
 - 6VUG 6VUG S L (+ 3 pdb)
 - 6PV7 6pv7 MULTIPLE UNP IDS IN SOME CHAINS
		S L S / S L S / S L S / S L S / S L S / ( + 4 PDB not UNP)
 - 6g79 6G79 MULTIPLE UNP IDS IN SOME CHAINS
		S / S / S L / S all UNP
 - 7jgc 7JGC S L S SSSSSSSSS(9) TOTAL 12 CHAINS ALL UNP
 - 6S8N 6s8n SSSSL all unp
 - 6ycx 6YCX SSSLLS



Examples (from Jaim's pdbRecNames server)

4uqf 10 chains all dbref1/2 (none dbref).
4you homotrimer

Sometimes dbref1/2 are interspersed between dbref records, e.g.
2iy3 

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getUniProtID() is in moltab.js
It is called by makeUniProtChains() in help2.js (for sequences)


I decided to handle DBREF1/2 in Sequences for the links to UNP.
See getLongUniProtIDs()