move out task pool from session

Add: apl v2 license header

Fix: Send multiple pkgs repetitive by tcp(issue AlexStocks#42)

Add: listen on random port

Imp: using writev

Fix: client do not block when server panic

Fix: create a new connection when can not get one by rpcClientArray.Get

Mod: version

Fix: issue 27

Merge pull request AlexStocks#28 from AlexStocks/fix/issue27

Fix: issue 27