fs: improve error messages

* Include a description for the error message
* For rename, link, and symlink, include both the source and destination
  path in the error message.
* Expose the destination path as the `dest` property on the error object.
* Fix a bug where `ThrowUVException()` would incorrectly delegate to
  `Environment::TrowErrnoException()`.

API impact:
* Adds an extra overload for node::UVException() which takes 6
  arguments.

PR: https://github.com/iojs/io.js/pull/675
Fixes: https://github.com/iojs/io.js/issues/207
Closes: https://github.com/iojs/io.js/pull/293


Reviewed-by: Ben Noordhuis <info@bnoordhuis.nl>