Negative seed values now consistently trigger “random” seed generation.

A negative value will create a random number seed using the current process ID and current time.  Traditionally, a configured value of 0 using either CL setting (-seed) or the configuration file (RANDOM_SEED) would trigger this behavior.  At this point in time, the Apto Random class treats 0 as a legitimate seed value and negative seeds as requesting time/pid generation.  This update makes it possible to set negative seed value at the command line and updates the configuration file description for RANDOM_SEED to note that a negative -1 (now the default) to trigger “random” seed generation.

I updated the AvidaConfig file to included the correct way to generate a random seed.
Merge branch 'master' of https://github.com/devosoft/Avida

Merging local changes with remote.