1. support save cal data in nvs;
2. support use phy partition to store init data;
In old SDK, we use (max_sec - 3) as init data sector, and (max_sec - 4) as cal data sector. This is changed in IDF style SDK, and these 2 sectors can be used for other perpose.
1. support generating esp8266 specific bin when input 'make' and so on
2. support 'make flash', 'make monitor' and 'make monitor flash'
3. esp8266 do not support secure boot