Add configuration page to web interface

[skickar]

Web interface lacks a configuration page. The menu should allow the user to control:

Set Client or AP mode: Allow connecting to Wi-Fi network for data access/remote control
SSID name: Change the Wi-Fi name of the soft AP the Nugget creates or joins
Password change: Change the password of the soft AP the Nugget creates or joins
Default Script: Select a script to auto-run on start
Hide USB drive: Toggle USB drive to appear or not by default
Neopixel brightness: Select brightness level for neopixel

[AlexLynd]

Updated this with a quick-fix config file on the USB drive.
Just create usbnugget.conf and add the network: and password: parameters on new lines to change the AP creds.