Add a TODO about toggleable map overlays
stats: Various fixes & a new graph, of enemy fighters
data: Slightly improved Stirling's accuracy
Added a new ftrbase.  Breaks saves!

To manually upconvert, change FBases from 11 to 12.  If you really want
 precise conversion, increment the first value after the colon in fighter
 records (ie. 'Type 0:1,blahblah' -> 'Type 0:2,blahblah')
Added navigation wobble and fuel exhaustion crash for fighters
A collection of changes to game logic & data, which together rebalance

Flak and fighters are much more deadly, but the budget is higher and damage is
 repaired more quickly (and serviceability actually equilibriates above its
 nominal value).

The intention is to try and make loss-rates more historically realistic.

Playtesting will be required to ensure that overall balance is OK.