remove empty /src folder
HTTP module: use unique integer identifier for connections and tasks instead of hex address

some minor changes:
- use %l logging format for abbreviated level, i.e. I for INFO, W for WARN etc...
- remove some spaces
clear keep-alive connections on cancelAll()

do not print warnings on "cancel" error codes
support for --http-version command argument, HTTP/1.1 is used by default
review restful and websocket services

- add GetDeviceData method and callback
- websocket: enable ping/pong messages by default (can be disabled with --no-ws-ping-pong command line argument)
- restful: keep tracking active HTTP tasks
stop processing on some control frames (such as CLOSE, PING and PONG)
use StreamDevice abstract interface and its first StreamDevice::Serial implementation instead of direct serial port connection
simple gateway: introduce TCP socket as a stream device