Starfield modification to randomly generate stars

Starfield now generates stars at startup rather than load them from the
server - approx. 50msec to load 50,000 stars.

STAR_COLORIZATION const in Generator.cpp is used to defined how
colorful the stars should be.

STARFIELD_NUM_STARS and STARFIELD_SEED sets the number of stars and the
random number seed used to generate the starfield.
Merge pull request #1083 from lordwaym/mod-starfield

Starfield modification to randomly generate stars