Add Adafruit WINC1500 WiFi shield

[martinjlowm]

This PR adds the Adafruit WiFi shield as a target: https://learn.adafruit.com/adafruit-winc1500-wifi-shield-for-arduino

[gschorcht]

The problem of wrong baud rates described in issue #44 is a common problem that occurs with any kind of ATWINC1500 hardware used with Arduino-compatible boards. Users that are trying to update the firmware for breakout boards such as Adafruit ATWINC1500 breakout or the Watterott ATWINC1500-Breakout will run into the problem that the programmer is not responding.

Therefore, the list should be extended with entries for a more generic device, e.g. AWINC1500 generic device, instead of adding entries for each specific device. There should also be a note in the `README.md' that says what these generic entries are for.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Martin Jesper Low Madsen seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}