Giant commit, testing to follow.

1. Re-parameterize p_ei, p_ir, and p_rs transition probabilities to make non-uniform temporal
spacing more straightforward.
2. steadyStateConstraintPrecision < 0 indicates that we should ignore this constraint entirely to save time.
3. Add facilities for gamma_ei, gamma_ir (new parameters)
Start work updating scripts, bug fixes.

Validation work next before more script updates.
Work on updating docs to reflect reparameterization
Bug fixes
Make singleLocationTest priors informative for latent and infectious times (well known quantities), fix gamma distribution parameterization issue.
Documentation update
Merge branch 'probability-reparameterize'