Support for downclock on AVR μCU's.

As stated in the README.md if you downclock you AVR MCU SlimLoRa adapts the receiving windows.

Partially tested only with RX2 windows.

Calculated delay:

2370159	div_2 RX2 ok on HLM 2s
1185079	div_4 RX2 ok 50% success on HLM 2s normally: 1185079.5
 592539	div_8 RX2 on HLM 2s	normally: 592539.75
 148134	div_32 RX2 ok on HLM 2s	normally: 148134.9375 baud rate 300

Also added a DEBUG_LED option so you can check with the variable MACreceived if you received a MAC command via LED or via Serial.print.

Try to support EU_DR6 - not ready yet.

Some DEBUG things and tweaks.

More EU DR6 corrections and ADR back off - UNTESTED

1. Downlinks on EU DR6 are not working. Investigating. TTN supports EU DR6, Helium does not.
2. Some better ADR back off code but it's UNTESTED

Update erase session utility

0.6.10

Update example

SF7BW250 support and NbTrans public

1. EU DR6 aka SF7BW250 support.
2. Moved NbTrans variables to public
   2b. application can know with if NbTrans_counter == NbTrans that we can send new message.

Version bump

Sorry for that, still confusing git and tags..

Margin report in device status must be ok now

1. Margin report in device status must be ok now
2. EPIC bug with #endif in LORAWAN_KEEP_SESSION in RfmSendPacket function fixed.
3. Debug is less verbose, but again verbose.

Handle null port on downlink - try to resurrect platformio

1. Handle null port on
2. Now, probably MAC commands with donwlink data must be
3. Platformio is stuck at version 0.1.9 for some reason. Added library.json in hope that will
4. Changed the interface of functions to store frame counter data.

Some gremlins for downlink data to be checked

I am not sure that everything is fine if MAC commands are mixed with application data.

NOT FULLY TESTED - Bug fix release

UNTESTED: RX2 DR window.

Important bug fix release with buffer overflow protection on downlink. Also added an example with downlink. Both tested and working.