CredentialManager for ESP8266 or ESP32

Stores ssid,password value pairs in flash memory. Automatically connects to a network if credentials were previously stored.

TODO

• Remove ESP8266WifiMulti dependecy.
• Read networks from FLASH and store them in RAM.
• Scan networks, try to connect to available networks, priority to > signal.
• Store previously used networks, and try to match existing networks to that.