Advanced screen, warning fragment

OpenKeychain/src/main/res/raw/advanced.md

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+[//]: # (NOTE: Please put every sentence in its own line, Transifex puts every line in its own translation field!)
+
+Advanced screen allows you to
+* share key in non-recommended ways
+* edit identities
+* edit subkeys
+* examine certificates in detail
+
+Only proceed if you know what you are doing!