Fix spacing

 * All should implement Clone, Display, Error, Debug, Send, Sync, 'static.

 * When we wrap an inner error, we always include context information describing what was happening when the inner error occurred.  This means that we should usually not `impl From<TheirInner> for MyError`.

 * Whenever appropriate, we have a `pub fn kind(&self) -> ErrorKind` function.

 * When a  public function can fail for a number of reasons that are much more limited than the crate's entire Error type, we should consider give that function its own Error type.

 * When a public function can fail for a number of reasons that are much more limited than the crate's entire Error type, we should consider giving that function its own Error type.

 * We use `Box<>` as needed to keep the size of the enumeration fairly small.

 * We allow more instability in these types than we allow in arti_client: these types should be inaccessible from the arti_client when "error-details" is not enabled.