make this internal
where line is something like " 53 HIS ( 53 ) A12" ignore xxxxI Cyy xxxx is 4char resno, I insertion code, C chain id, yy is model number
return a residue spec, or #f
A problemed-res-list is improper pair where the car is a pair of string, one describing the problem, and the other being the "fix it" button label. The cdr is a list of residue specs.
A problemed-flip-list-list is a list of those things.