add brms to multi-trait models?

[bbolker]

right now we have

Multi-trait analysis: (multiple dependent variables) BMTME, MCMCglmm, MegaLMM

We should

• add brms
• indicate which of these packages can do multi-type models (i.e. multivariate responses with different conditional marginal distributions for different outputs)
• maybe also add that many flexible (G)LMM packages can do multi-trait analysis by 'melting' data into long format; e.g. example here (is there a better/more canonical reference for these, e.g. a package vignette somewhere?)

[bbolker]

also INLA, according to Alain Zuur.

[bbolker]

bac839b