Start on ship library shipdata display
A bit more prototyping of the ship library system

Add shiplibrary.plist to replace and extend demoships.plist
Give automatic but overridable speed, turn rate, cargo values
Add a few test entries to shiplibrary.plist (very unfinished)
Automatic and manual entries for shiplibrary
Remove witchdrives from a couple of ships which really shouldn't have them
More controls and entries for the ship library

- Categorise and sort ship entries
- All four arrow keys now used to navigate
- Entries for all conventional ships, with occasional redaction
(no Constrictor, intentionally)
- new screenbackgrounds entry since the format of the screen is changed