Move vignette

CRAN now requests vignette sources be in vignettes/ instead of inst/doc/.
Also remove unnecessary intermediate files created when building the
vignette.
Make useDefaults and unDefaults defunct

Make useDefaults and unDefaults defunct, since they could possibly modify
functions in other namespaces.  Comment them in all the documentation
examples (since they now error).

Also remove supporting functions: usingDefaults, .importDefaults,
useDefaults.original, unDefaults.original.
Update version and maintainer
Avoid partial argument matching

R CMD check complains about partial argument matching.