settings

Added load & save settings.
save_settings () = stores data in the EEPROM.
load_settings ()  = loads data from the EEPROM and sets global_time to
the value read from EEPROM.
settings.c

added settings object
EEPROM & Debug

removed the declaration of global_time in main and moved it to
settings.c.

In the interrupt routine, added some debug output to USART.
inclusion of settings

Using settings functions to save and load new settings