EEPROM emulation in flash
All user data stored in user_conf structure.

macro/constants:
FLASH_CONF_START_ADDR - start address of flash page used
maxnum - maximal amount of structures in data

Call function get_userconf() at the beginning of your code after base initialisation. It will copy data from last non-empty flash storage to variable the_conf (or leave the_conf empty if all flash is clean).
Change some data in `the_conf` and after it call store_userconf() to save data in flash. This function returnc 1 in case of error. It will clear the flash page if all indexes used and store at first.
