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.

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.

(cherry picked from commit 29dd7fd472)

Allows more flexibility downstream

Also some minor documentation and naming changes for consistency.

And keeping only most basic SMS

problem was new lines, not time.

Is there a way to force it to return in smaller chunks?

Also fixed the "isNetworkConnected" for ESP8266

Also shorted time between checks in "isNetworkConnected" for all modems

- fixed int/uint warning
- added functions to get local IP address with esp8266
- fixed local ip fxn for xbee
- removed extra test builds
- set travis to build all modems in tests