message: Implement Debug/Display for PropertyList
diff: +use std::fmt;
  +
  use ffi::h5i::{H5I_GENPROP_LST, H5I_INVALID_HID, hid_t};
  use ffi::h5p::{H5Pcopy, H5Pequal};
  @@ -9,6 +11,22 @@ pub struct PropertyList {
  handle: Handle,
  }
  +impl fmt::Debug for PropertyList {
  + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  + fmt::Display::fmt(self, f)
  + }
  +}
  +
  +impl fmt::Display for PropertyList {
  + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  + if !self.is_valid() {
  + "<HDF5 property list: invalid id>".fmt(f)
  + } else {
  + "<HDF5 property list>".fmt(f)
  + }
  + }
  +}
  +
  #[doc(hidden)]
  impl ID for PropertyList {
  fn id(&self) -> hid_t {
  