* Allow definition of custom network interfaces
* Create network client interface class
* Change to PIMPL approach
* Add example for custom network clients
Why:
- Show users how to use multiple network interfaces
This change addresses the need by:
- Adding an example PIO project to use Wi-Fi and GSM/LTE
* Add WebSockets prefix to normal and secure client
Why:
- Avoid name collision
- Fix broken reconnect change
This change addresses the need by:
- Adding WebSockets prefix to all custom clients
- Marking custom client as secure in clientDisconnect()
- Remove broken fix for reconnecting
