Shorten really long engine descriptions (#2886)

* Shorten really long engine descriptions

Also added localisations for some of the longer engines that needed it.
Hopefully it's fine to switch to plume and sound from Waterfall, as it's a bit shorter.
Viking (5/6) and the AJ260 radial will need scroll bars until I finish localizing ROE
Currently, only the NAA75, LR89, LR105, Agena, RD58, Castor 4 and AJ260 SL radial have scroll bars, and those descriptions have all been shortened significantly.
Removed advice on how to use an RL10 as that should be clear from its stats.
In general, some review would be nice. I've tested it, but I have had to elide some information and want to make sure I'm not removing too much

* Correct grammar and things I missed

* Make NK's suggested changes