Add timeout parameter for connections

[stlehmann]

For some reason one might want to set a timeout for establishing a connection or recognising a broken connection. ads.set_timeout does that (https://pyads.readthedocs.io/en/latest/pyads.html#pyads.ads.set_timeout) .. or should do that. Would be nice to implement this as a new parameter to Connection.__init__.

[shanek-maker]

Absent this, the default seems to be ~70 seconds and blocking. The problem seems to present when the host has dropped offline and I'm either checking the status (via PLC.is_open, and/or PLC.read_state()[0] or reading/writing to the host.