Support reading and writing file attributes

[streamich]

What is the problem this feature will solve?

All operating systems provide a mechanism to store and read Extended file attributes, provide an API to read/write/delete file attributes.

The attributes can store metadata such as the unique file ID (which is retained even if the file is moved), file version, mime type, checksum, contents encoding, etc.

The API could be part of the FileHandle interface:

• FileHandle.prototype.readAttributes()
• FileHandle.prototype.readAttribute(name)
• FileHandle.prototype.writeAttribute(name, value)
• FileHandle.prototype.deleteAttribute(name)

What is the feature you are proposing to solve the problem?

Extended the fs API with ability to read and write file attributes.

[himself65]

Upstream: libuv/libuv#234

[himself65]

Duplicate: #857

Suggesting we close until we can use new functionality provided by libuv.