RuleNotFound error does not show meta

[bartvanerp]

So it might occur that you forget to specify meta in the @model macro. We then will get a rule-not-found error like:

@rule ContinuousTransition(:x, Marginalisation) (q_y::PointMass, q_a::MvNormalMeanCovariance, q_W::Wishart, ) = begin 
    return ...
end

whereas it looks like one is defined already:

ContinuousTransition(m_y::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T)
ContinuousTransition(m_x::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T)
ContinuousTransition(q_a::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T, q_W::Any)
ContinuousTransition(q_a::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T, q_W::Any)
ContinuousTransition(q_y::Any)
ContinuousTransition(q_y_x::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T, q_a::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T, q_W::Any)
ContinuousTransition(q_y::Any, q_x::Any, q_a::Any)
ContinuousTransition(q_y_x::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T, q_a::Union{MultivariateNormalDistributionsFamily{T}, MultivariateGaussianDistributionsFamily{T}} where T)
ContinuousTransition(q_y::Any, q_a::Any, q_W::Any).  <--- this one :)
ContinuousTransition(q_x::Any, q_a::Any, q_W::Any)

This is confusing, so we probably should include meta.

[bvdmitri]

Fixed in #495