[optim] adds lookup for previously identical haplotype + time
adds const [] accessors to matrix
Update to multiple times for F using a heirarchical model.

Model is F[i] ~ Normal(Alpha[i], Tau[i])

where priors on Alpha, Tau are

Alpha[i] ~ Normal(0, 0.1)
Tau[i] ~ Gamma(0.1,0.1)
updates R code for heirarchical model for F
switch to a matrix for hyperpriors
switch gibbs_ar1 to ar1 with mean 0, suitable for residuals
use 1..T for times in human file rather than 0..T-1
[optim] updates of F are per time/per source, so recalculate likelihood with this in mind
[cosmetics] various cosmetics/comments
move likelihood storage to where it's used
update to AR(1) process
update R source for AR(1) process and prettier graphs