Introduces support for multiple DBOB versions simultaneously.
The property fd.dbob.SIZE.version now takes a list of
version numbers separated by a colon (e.g. 120:118:110), which
builds a search path through these versions of DBOBs when a
SkyMap for a particular revolution is requested.
Brought up to date, using the latest versions of ISOC support libraries (e.g. isoc-util)