Add option to save freqs of selected allele at selection start

Added option to save freq of selected allele in each pop when selection starts.

Fixed bug in --genmapRandomRegions

Randomization was not done for first simulate.

Added option to save sampled model parameters.

If environment variable COSI_SAVE_SAMPLED is set to the name of a file, sampled model parameters will be saved to that file.

Initial support for selection on standing variation

Initial implementation of simulating selection on standing variation. Work in progress.

Added tped support

v2.02

cosi2 version with tped