Include seasonality about seir_covid19_dev HOT 3 CLOSED

We don't have great reason to hope for seasonality (in year 1--i think maybe we do expect it in subsequent years) but want to include sliders so we can play out scenarios. To set defaults could use:
For northern temperate regions:
ε seasonal forcing: uniform .25-.75
θ peak transmissibility: normal peak at 0; sd .1
taken from the bullet points on page five of neher et al.
Mike
Neher_seasonality.pdf

from seir_covid19_dev.

epsilon<-.5
theta<-.1
in model:
seasonality<- (1 + epsilon * cos(2pi(t-theta)))
b1<-b1seasonality
b2<-b2seasonality
b3<-b3*seasonality

from seir_covid19_dev.

There is now a script to runSpreadSeason.R that runs the dynamics with seasonal variation in the Beta values (same for all Betas). Note that time is in days so the correct function is:
(1 + seas.ampcos(2pi*(t-seas.phase)/365))
Seasonality affects all Beta values equally right now

from seir_covid19_dev.