docs: Add some missing obsolete documentation

Acquired from the JAC vaxes:

 SUN/6  - AATGS
 SUN/10 - ARGSLIB
 SUN/51 - Submitting NEWS items
 SUN/60 - IRAS Image Analysis
 SUN/64 - MONGO
 SUN/74 - DSCL Starlink Command Language
 SUN/79 - CDS
 SUN/80 - IRAS - Extended emission and pointed observations
 SUN/81 - LRSEXT
 SUN/89 - APLATE
 SUN/97 - REXEC