[GZG] [FT] Tactical jumps

To help explain the usual set up for FT battles (ships arrive on the table
relatively close to opponents, at speeds of less than that provides by a
couple of turns of accel), I'm proposing that we have rules for tactical
jumps. A tacjump will displace the ship by a distance of a few lightseconds,
and has a cycle time of a few turns (as
opposed to the hours needed for a multi-lightyear jump). Note that it is
usually not possible to disengage from combat by means of a tacjump--the
opponent can re-acquire and jump after you.

A tacjump does have a chance of misjumping, which is increased by short prep
time, poor crew quality, and momentum of the jumping ship (a mass 10 scout can
safely jump at higher speeds than a mass 250 SDN).

Misjumps only affect the jumping ship, unless you arrive at a point at the
other end which is already occupied. However, tactical jumps have an inherent
distance deviation, so you don't dare bunch your ships too closely.