OTA Firmware Update

[sidey79]

Support a method to flash Firmware via http directly to the ESP.

Some hints how to implement this:
http://s6z.de/cms/index.php/homeautomation-homecontrol/hardwareplattformen/esp8266/133-ota-esp8266-over-the-air-flashen

Firmware should be provided via FHEM to the ESP, so the ESP itself wouldn't need direct internet access.
The update server could be startet via new control command.

Needs some ideas how can secure the update against malware.