resolve PDBEntry and DBRefs from older jalviews with PDB IDs with appended chaincode

Earlier versions of Jalview allowed the user to specify the specific chain to be used to map to a sequence by appending the chaincode for a PDB ID. These result in PDBEntry objects with IDs like '1QIPA'.

The new PDBEntry/DBRef validation for primary sequence accession refs (JAL-2106), means that for a sequence with a primary reference of PDB:1QIP, if a PDBEntry like '1QIPA' is present, 1QIP will not be recognised as the sequence's primary reference, which may cause issues with cross-refs.

This is an unresolved component of JAL-1803.