3.9.13 20170210
* Add FlashChipSize to Status 4
* Removed redundant DHT2 option and code
* Add Sonoff SV GPIO pin 05 configuration (#40)
* Add configuration file backup and restore via web page
* Fix latency due to light_sleep mode even if sleep was set to zero
(#50)
3.9.12 20170208
* Fix compile error when webserver is disabled (#30)
* Fix possible ESP8285 flash problem by updating Flash Chip Mode to DOUT
during OTA upload
* Fix hostname issues by not allowing user entry of string formatting
and removing from user_config.h (#36)
3.9.11 20170204
* Fix command I2Cscan
* Fix not allowed spaces in Topic, ButtonTopic and SwitchTopic
* Make all TELEMETRY, STATUS and COMMAND message topics unique (#4)
* Advertise command topic to be used by iobroker (#299)
* Fix butten (non)detection if no GPIO_KEY1 is defined (#13)
* Change WeMo serialnumber from 7 decimal chars to 8 hexadecimal chars
(#18)
* Update web page with Build Date/Time, Emulation and mDNS Discovery and
Advertise information (#21)