Godot bind update

[ClintonSarkar]

Added two new methods that read and write strings between godot and socket.

[Abdera7mane]

Godot already has StreamPeer::get_string() & StreamPeer::put_string() to read/write a Godot string which is not really useful unless both server and client are Godot applications, so I understand the purpose of the patch you introduced. However StreamPeerUnix::read() & StreamPeerUnix::write() can be replicated in GDScript:

var stream = ... # instantiate and connect to a UNIX socket

# reading
var length = stream.get_available_bytes()
var buffer = stream.get_data(length)[1] as PackedByteArray # the first element contains an error code
var message = buffer.get_string_from_utf8()

# writing
stream.put_data(message.to_utf8_buffer())

further more, this approach is not restricted dealing with UTF8, you are free to store the string in ASCII, UTF16, UTF32 etc...