Reprogrammable thermostat timing and temperature from telnet client

Store and restore thermostat values from EEPROM to survive power outage.

Ethernetclient client becomes a global variable.
Set points and timings no longer hard coded.
Decrease hysteresis

Found temperature sweep was too big to be comfortable, reduced from 1
degree to 0.4 degrees because the heater stays hot and continues
radiating after it has been turned off by controller.