added AIndexSelection base class
implementation of fitness proportional selection operator
optimized some loops
fitness proportional selection: allow duplicate indices in selection
fitness proportional selection: changed 'spin range'
added MersenneTwisterUniformIntDistribution class
caching distributions in MersenneTwisterUniformIntDistribution::get_number(min, max) method
implementation of tournament selection
implementation of double-tournament selection
merged AnsiRandomNumberGenerator source and header file to s single header
optimized loop in double-tournament selection operator
implementation of 'fittest' selection operator