Catch occasional problem with docking AI frustration

Requires station to be destroyed at inconvenient time.
Revert directory creation on Windows
Fix some variable-defined errors in priority AI
Mission instructions: merge lists with identical headers
Fix the remaining font assumption

Two new parameters to oolite-font.plist (default to the 1.80 hard-coded
values if not set) "f6KernGovernment" and "f6KernTechLevel". Fonts with
proportional numbers should set the latter to 0.0.
More docking fixes

- Fly away from destination will now turn if pointing right at the coordinates
- if max_cos is increased, min_d is decreased to allow course corrections to be carried out
- minimum approach to coordinates speed reduced for docking
Precautionary fix

Ships with high speed/roll/pitch might need even more slowdown
Merge remote branch 'upstream/master' into shader_update