Fix: Prevent AlphaFold 1x1x1 dummy cell crashes

[KevinBattaile]

AlphaFold inserts a CRYST1 line with a cell of 1 1 1 90 90 90 P1 that causes rwcontents to then crash because the contents can't possibly fit into that cell.

This fix has a pre-processor block to detect these small cells in search models and replace them with a much larger cell prior to downstream processing. This then prevents rwcontents from crashing. The inevitable difference in the unit cell and space group from the input MTZ file will result in a phaser-mr run, which is the expected behavior

The original fix for this was to remove the CRYST1 line, which would result in going to phaser-mr, but a recent update using gemmi to read the pdb file results in the CRYST1 line being written back and rwcontents failing.

[KevinBattaile]

Just pushed an update to handle PDB files downloaded from RSCB.