Move SASL external documentation into documentation.

This is just copied directly from the source file which was deleted, so
it's not lost in version control limbo.

documentation/SASL external.html

@@ -0,0 +1,27 @@
+/**
+ * Implementation of the SASL EXTERNAL mechanism.
+ *
+ * To effectively use this mechanism, Java must be configured to properly 
+ * supply a client SSL certificate (of some sort) to the server. It is up
+ * to the implementer to determine how to do this.  Here is one method:
+ *
+ * Create a java keystore with your SSL certificate in it:
+ * keytool -genkey -alias username -dname "cn=username,ou=organizationalUnit,o=organizationaName,l=locality,s=state,c=country"
+ *
+ * Next, set the System Properties:
+ *  <ul>
+ *  <li>javax.net.ssl.keyStore to the location of the keyStore
+ *  <li>javax.net.ssl.keyStorePassword to the password of the keyStore
+ *  <li>javax.net.ssl.trustStore to the location of the trustStore
+ *  <li>javax.net.ssl.trustStorePassword to the the password of the trustStore
+ *  </ul>
+ *
+ * Then, when the server requests or requires the client certificate, java will
+ * simply provide the one in the keyStore.
+ *
+ * Also worth noting is the EXTERNAL mechanism in Smack is not enabled by default.
+ * To enable it, the implementer will need to call SASLAuthentication.supportSASLMechamism("EXTERNAL");
+ *
+ * @author Jay Kline
+ */
+