21.9: Adding new flag for forcing use of local geometry files for development

Following discussions with @goblirsc. Adding new flag for forcing use of local geometry files for development purposes, rather than just relying on choice of geo tag as to whether we take the layout from the DB. Improved error handling for unsupported geometries or missing local files (prints more informative messages which will hopefully help to make it clear what the issue could be, and will bail out already on discovering a bad configuration, which saves a bit of time waiting). Setting default value of doGMX which should normally be True.

FYI @goblirsc @lmijovic @fcostanz @npetters @nova @hhayward @asalzbur @jfoo @hessey