New MM firmware released for Avalon4, Hardware model: MM-4.0, Version: 401502-d517e210

Firmware Details:
    http://downloads.canaan-creative.com/software/avalon4/mm/2015-02-14/

ChangeLog:
* Add a bootloader feature, auto reboot after download
* Feed watchdog when get package because it's a block function
* Fix system crash when modify the miner_id by unintentionally
* Change compile flag from MBOOT to BOOTLOADER
* Support mm config load & save

Fengling