S3-generic function to use with models which contain several groups of
coefficients in their coefficient vector. The `coeflist`

methods
are intended to list the coefficients by group. The default method
simply `split`

s the coefficient vector given the number of
coefficients by group.

## Usage

```
coeflist(x, ...)
# Default S3 method
coeflist(x, npars, ...)
```

## Arguments

- x
a model with groups of coefficients or, for the default method, a
vector of coefficients.

- npars
a named vector specifying the number of coefficients per group.

- ...
potential further arguments (currently ignored).

## Value

a list of coefficients

## Examples

```
## the default method just 'split's the coefficient vector
coefs <- c(a = 1, b = 3, dispersion = 0.5)
npars <- c(regression = 2, variance = 1)
coeflist(coefs, npars)
```