Skip tests for RAK11200 until BSP is updated ('class HardwareSerial' has no member named 'onReceive')

fix: docs and example of user AT commands

Fix timer bug. If timer is restarted with a new time, there was a bug that actually stopped the timer

Update at_cmd.cpp

Updated the `at_query_p2p_config()` function so that the string displays the exact same configuration string as what the user sends. Right now, we pass BW as "125" for instance, but the query function sends back "0":

```
AT+P2P=868000000:10:**125**:1:8:22
OK
AT+P2P=?
+P2P:868000000:10:**0**:1:8:22
OK
```

I think it's better to output the same thing the user sends.

Fix AT-Commands.md
@Kongduino 
Thank you!

The paragraph about `AT+PTP` was a copy-paste of `AT+PCR`. Fixed that.