extended simple feature and repeat feature calls on slice to allow connection to a non-"core" database

New routines to generate the display_xrefs and gene descriptions. This was done incorrectly before or at least inconsistently. Still need to remove comments etc but saving this version for backup

genebuilder-standard optional options added ( -host || -dbhost etc.)
-additinal option -dbname added

treeshrew and hedgehog added

minor problems (e.g. whitespace after a line-continuation \)

from the sequence-match xref pipeline (they are too for this to be
sensible)