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Should there be an extractor function for the mean square error?  If
  so, what should it be called? (There is now a "sigma" extractor.)
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Determine why the names of the components of the values of
the ranef and coef extractor methods are not printed. (Done by
changing from S4 classes to S3 methods.)
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Collapse repeated grouping factors and correspondingly modify the
ranef and coef methods.
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Add an element to the deviance slot to hold sigma or log(sigma).  The
interpretation will be that an NA value means to use the conditional
estimate of the scale parameter.  For a generalized linear mixed model
without a scale parameter set sigma = 1 (or log(sigma) = 0) and put
constraints on the parameter so that it is not estimated.

Upon convergence replace that element with the conditional estimate in
models where it has been profiled out.
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Currently lmer does not fill in the disc and bqd slots in the deviance
slot.  Fix this.
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Remove unused symbols from src/Syms.h and src/init.c
Add symbols to src/Syms.h for names currently accessed through install().
Replace the glmer_create and nlmer_create C functions with R code.
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- Revive the "lmer" and "glmer" classes.  Slots like "family" should
  be in "glmer" only.  Many methods for "lmer" can be simplified as,
  for example, they will always use the scale factor.

- Add a "pedigree" class and methods for it.  Allow a pedigree
  argument in lmer.

- change the status vector to an integer vector.  The steps are
  cumulative so we only keep track of the stage.  Also REML and glmm
  are stored here.

- anova method for lmer objects.  Will entail saving the terms
  attribute.

- Move large data sets into a MEMSS or mlmRev package

- Change Calloc/Free patterns in the calculation of bVar

- Re-write the ccoef methods in C

- Evaluate the likelihood of a fitted GLMM by the Laplacian approximation
