Two bugs in dogfight about chance to hit

1) Chance to hit a UFO should be adjusted according to UFO size, the
formula is CTH = (1+3/Size)/2*Accuracy, where Size is 5 for Very Small
to 1 for Very Large. This is how it was in original game, in OXC it is
just flat right now.

2) Projectiles try to impact again and again because missing does not
prevent a check for impact. Fixing this required changing the movement
code, because previously when projectile reached max range it would
immediately be considered to have missed, which would prevent
projectiles hitting at max range (for example, when cautious or standart
attack is chosen)
whoops
Merge pull request #874 from IstrebiteI/dogfight_fix

Two bugs in dogfight about chance to hit
primed grenade indicators.
fix builder error question mark.

also an unused var that's been nagging me.
smooth out grenade flashing
colourize numbers and shift positions
adjustments
fix xp thing
define UFO fuel in ruleset

because USOs use Zrbite
some TFTD infrastructure

slightly more dynamic loading of graphics, function for loading palettes from lbm files

horrendous hard coding in place here, disassociating surface names from file names

sprite recolouring disabled for aquanauts for the time being.
add depth to battlescape

please note: TFTD is still not supported.
tanks only base defense woo
fix a one in a million AI bug