Demonstrations for emulated EEPROM program and erase operation.

Prerequirements:
(1)define a virtual address for each data need to program into emulated EEPROM;
    /* virtual address define, 0xFFFF is not allow */
    uint16_t g_VirtAddTab[VAR_NUM] = {0x2222, 0x4444, 0x5555, 0x6666, 0x8888};
(2)decide which BANK to use;
BANK0 contains page 0 and page 1;
BANK1 contains page 2 and page 3;
each page's address, please refer to "emulated_eeprom.h".

1. Demo 1 : only use BANK0 to save data;
2. Demo 2 : only use BANK1 to save data;
3. Demo 3 : use BANK0 and BANK1 to save data;
Each demo do the same thing: write the data to its' virtual address, then read back and check it's value.