Added executor-available?
Added waiting-next-handler
Added simple server framework library (net server)
Changed atomic unit for execute-future to avoid dead lock.
Added test case for executor-available?
Changed waiting handler name to wait-finishing-handler
Addes max-retry slot to <server-config>
Expose <simple-server>
Added test for (net server)
Added server-stopped? procedure for diagnosis
Fixed error sending close notify to closed peer (from server to closed client)
Added tls-socket-shutdown
Added stopper socket slot to <simple-server>
Added TLS socket test for (net server)
Removed guard and added has-peer? slot to check if shutdown should send close notify.