ParamsWithStats: `lp` or `logjoint`?

[penelopeysm]

I messed up and made one method lp and one logjoint:

DynamicPPL.jl/src/chains.jl

Lines 84 to 86 in 8e359ce

	logprior=DynamicPPL.getlogprior(varinfo),
	loglikelihood=DynamicPPL.getloglikelihood(varinfo),
	lp=DynamicPPL.getlogjoint(varinfo),

DynamicPPL.jl/src/chains.jl

Lines 130 to 132 in 8e359ce

	if has_prior_acc && has_likelihood_acc
	stats = merge(stats, (logjoint=DynamicPPL.getlogjoint(varinfo),))
	end

Should probably choose one and stick with it.