Gets the path to the file cache directory. If missing, the directory is created.
# S3 method for default
getCachePath(dirs=NULL, path=NULL, rootPath=getCacheRootPath(), ...)Returns the path as a character string.
  If the user does not have write permissions to the path, then
  an error is thrown.
A character vector constituting the path to the
     cache subdirectory (of the cache root directory
     as returned by getCacheRootPath()) to be used.
     If NULL, the path will be the cache root path.
(Advanced) character strings specifying the
     explicit/default cache path and root cache path.
Not used.
Henrik Bengtsson
setCachePath.