Restart timer plus plus

[btsimonh]

A variety of improvements which allow the client to reconnect in different circumstances. e.g. on pigpiod restart, turning wifi off on laptop, and then back on again, etc. Not tested with laptop sleep. Also adds an option to keep node alive, addresses https://github.com/guymcswain/pigpio-client/issues/42 Also, if timeout is -1, it will try forever.

br, Simon