Store the server address in the SSS3's sd config and accept other registration parameters through a webpage

[Jepson2k]

Store the server address in the EEPROM. Any new SSS3 device will first attempt to connect to the server and retrieve the registration JSONs before presenting its registration and configuration webpage. If connection to the server fails it should use a basic registration JSON stored in memory to display the registration page. After the user inputs the registration, if the server continues to be unresponsive, the SSS3 should continue to attempt connections (about once per minute) to the server until it is available.