Consider adding network section

[Valera]

Hi!

I noticed several things:

• There is websockets section.
• There is no general network section.
• usocket library is :star:-ed in websockets section, but actually there is no support for websocket protocol.
• iolib is marked as «I/O library» and that is perfectly true, but nobody will find it searching for sockets or networking.

I suggest

• Creating network section, moving iolib and usockets there
• Making a reference to websockets section from network section.
• Setting more searchable description for iolib such as «socket library, a DNS resolver, an I/O multiplexer, a pathname library and file-system utilities. Supports only Linux and FreeBSD.»