added socket out parameter to multiplexer

The multiplexer will now return the socket the event originated from
together with the event.
Added UdpSocket.State

Added UdpSocket.State so that the state of the socket can be checked
from the user thread
Removed "None" SocketState option
Added UdpSocket.PrecisionTime property
Removed old assembly titles, changed version num
Removed using statement from AssemblyInfo.cs
Renamed Stats property to Statistics
Changed HeaderBitSize and added some comments

HeaderBitSize now uses the constants from UdpHeader for calculating it's
total size instead of the hardcoded 16 * 2
Changed internal code in UdpHeader

All the code in UdpHeader now uses the public constants instead of
hardcoded values
Comment changes
Bumped version to 1.6.3