New Bayesian identity threshold; updated documentation

[iainrb]

• New default sample pass threshold for Bayesian identity:
  • Posterior probability of identical samples must be greater than prior probability
  • Evidence of the QC plex check must make us more certain that samples are identical
  • Changed expected JSON output data to use new threshold
• Remove redundant Bayesian identity parameter defaults
  • All Bayesian identity defaults are now in SampleIdentityBayesian.pm
• Update changelog
• Fix Perldoc in ready_workflow.pl