docs/put_key: add tutorial that explains how to manage global platform keys
With the increased interest in using GlobalPlatform features of UICC and eUICCs (OTA-SMS, applets, etc.), also comes an increased interest in how the related GlobalPlatform keys can be managed (key rotation, adding/removing keysets from/to a Security Domain).
Unfortunately, many aspects of this topic are not immediately obvious for the average user. Let's add a tutorial that contains some practical examples to shine some light on the topic.
