Add NetworkServer

[PaulZC]

This PR:

• Adds the NetworkServer class which supports both WiFi and Ethernet
• Modifies PvtServer so it uses NetworkServer instead of being hardwired to WiFi
  • Resolves pvtServerStart hardwired to WiFi? #797
  • Includes keep-alive DNS calls for WiFi when no clients are connected - prevents disconnects due to ASSOC_EXPIRE
• Periodically displays the PVT / UDP Server IP address and port
  • This can be disabled if desired - via the Network menu (option 8)
• settingsToDefaults() calls checkMessageRates() to ensure the base and rover rates are correctly initialized - before being passed (e.g.) to the web config
  • Resolves Sparkfun Facet RTK bluetooth issue with profiles? #632
• Restructures pushGPGGA as per RTK Everywhere issue 695
  • Prevents ntripClient->write from gatecrashing ntripClient->read
• Restructures how Events and ARP are written to the ubxFile
  • Resolves handleGnssDataTask should write all available data to SD card #796
• Adds PR make log message match L-band disable function name #794 - thank you @edgecase14

[PaulZC]

I tried an overnight log test, logging the standard rover messages at 4Hz with ARP logging at 0.1Hz. The log is completely clean: