kaplibs: Allow random number seed to be set by environment variable

Since kaplibs is used by several starlink packages, the environment
variable is STAR_SEED rather than KAPPA_SEED.
cupid: allow specified fellwalker walks to be dumped to NDF

Uses new config parameters DUMPPEAK and DUMPWALK
cupid: More fellwalker debug info
pubs: more details of the basic fellwalker clump finding process