Use seperate thread for signal handler and...
- use specific RT signal for UART
- block uart signal in main thread and allow it in reading thread.
Get back to poll functionality.
Do uart reading in run_sensors
Uart reading using epoll because it should be faster.
Use line triggered mode
Return result of poll.
Merge branch 'epoll' into dev

Merged with epoll version for easier start.
Test epoll with level triggered approach.