DF-5198 add comments and minor changes for IPAddress and Endpoint

rename enums
DF-5198 add Post and PostQuit methods to IOLoop class to allow queuing and executing user handlers from any thread

Introducing of these methods replaces need of AsyncRequest class
DF-5198 deep refactoring of classes DeadlineTimer, TCPAcceptor, TCPSocket and UDPSocket

They no more inherit to HandleBase class
DF-5198 change to TCPTransport: get rid of AsyncRequest
DF-5198 get rid of TransportFactory. Transports now are created in ChannelManager
DF-5198 remove unused file, sorry
DF-5198 move network library to DAVA::Net namespace
DF-5198 rename function NetworkErrorToString to ErrorToString as network lib has moved to namespace DAVA::Net