Average temp reading + ISP connector

Temp readings are averaged per second before comparing to the set
temperature. Added ISP header to board for on-board reprogramming.
Declared variable

Forgot to declare variable used for averaging temperature readings.
Added general HALT function and moved defines to .h file.
Moved from _BV(1) to direct 0x01 bit patterns.
Added halting easter egg.
Removed easter egg.
Harmonized HALT function
Fixed bug that allowed time reset while timer was running.
Updated schematic and PCB

Now includes 4th led for reading indicator. Moved ISP connector to more
accessible location.