getVignetteHeader(vig, field)
hasVigHeaderField(vig, field="VignetteIndexEntry")getVignetteHeader function will extract the metadata from a
vignette file and return it as a named list, where the names of the
list elements correspond to the metadata fields, and the elements
themselves the values. If a specific field is desired, it can be
specified with the 'field' argument. The hasVigHeaderField function is a simple wrapper around
getVignetteHeader and will most likely be removed in the very
near future. It just is a boolean to report if a given header field
exists or not.