[Therion] Splays in pdf plans

[Bruce]

>I only had one map in the file so was allowing therion to do its stuff with
no select option in the config file, also as the map has map information you
do not need to use -proj plan, it just works. So to get splays displayed as
the 'default' you need to select the map it is in (possible a high level one
would work but I have tried enough for now) and explicitly have  -proj plan
on the map group, otherwise you only get the centreline.

Thanks Andrew, that's a good tip for the wiki somewhere.