This function allows the user to examine and reset the values
  of global parameters which control actions in the
  spatstat package.
  It is analogous to the system function options.  The global parameters are:
  [object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
  
  If no arguments are given, 
  the current values of all parameters are returned,
  in a list.
  If one parameter name is given, the current value of this
  parameter is returned (not in a list, just the value).
  
  If several parameter names are given,
  the current values of these parameters are returned, in a list.
  
  If name=value pairs are given, the named parameters
  are reset to the given values, and the previous values of
  these parameters are returned, in a list.