Settings Implementation

Allows full configuration of Network, PIN and Door without editing or
even creating CFG files.
-Network will generate random MAC and use DHCP by default setting and
store into EEPROM if no NETWORK.CFG file is present
-Default pins.cfg file generated if not present
-RSV pins can not be assigned via Settings
-Free configuration of doors.cfg via web page, device updates only with
properly formed JSON
Randomly assigning a MAC address is nice, but I wonder if this isn't gold-plating. Is it really needed?
Current Ethernet shields come with a sticker indicating the MAC address you should use.
Even for older Ethernet shields I think this would very rarely be needed.
- If you have several Arduinos then you probably want to know which Arduino has which MAC address. In that case you would set them manually (an operation you only need to do once for each Arduino).
- If you have one Arduino then a hard coded MAC address will work fine.