support WiFi S6B no passwd

Also removed some extra stream-clear functions

They do need a millis() based timeout so that data left in the buffer after the socket closes can still be read in but the maintain doesn't sit and wait forever.

Only for modules that buffer the data internally

For loggers that return data "immediately" (unbuffered, data sent w/o request) read will "maintain" and look for any incoming data as long as the socket is open.  Use timedRead if you want a timeout.

For modems that buffer the response and wait for you to request data, read will stop if socket closes OR if there is no longer any data in the modem's response buffer.

And implemented for ublox

also removed some extra docs

Thanks to @Mikelanner

Should fix https://github.com/vshymanskyy/TinyGSM/issues/204