Infer panel for bad region when it's unambiguous
The latest CrystFEL version is fussy about requiring that the panel name is given for an fs/ss bad region in the geometry file. This has come as a surprise for many users, and there seems to be a lot of geometry files in circulation which don't include the panel name because it's "unambiguous" - either there is only one panel, or the data for all panels comes from one data block. In these cases, the parser should be a little more relaxed about things.