#243 Document "setinfo" option abbreviations

[Artur Tarassow]

The AI just suggest the following shortcuts for setinfo which are handy but not documented:

nulldata 10
series y = normal()
setinfo y -d "Some random normal" -n "Random"

Description:

• -d is an abbreviation for --description=string
• -n is an abbreviation for --graph-name=string

I am not aware of abbreviations for the other options setinfo involves.

I think, documenting at least the two above is useful for users.

Artur