immunity

Defines classes and methods for calculating immunity

Functions

check_immunity	Calculate people's immunity on this timestep from prior infections.
exp_decay	Returns an array of length t with values for the immunity at each time step after recovery
init_immunity	Initialize immunity matrices with all genotypes and vaccines in the sim
linear_decay	Calculate linear decay
linear_growth	Calculate linear growth
precompute_waning	Process functional form and parameters into values:
update_peak_immunity	Update immunity level