Add man entry for encryption script

tapeserver/cta-taped.1cta

@@ -141,6 +141,10 @@ The number of disk I/O threads.
 The protocol to be used when transferring files to and from disk servers.
 Possible values are RFIO or XROOT.  The value is not case sensitive.
 
+.TP
+\fBtaped externalEncryptionKeyScript
+The Python script to interface with the encryption data store.
+
 .TP
 \fBXROOT PrivateKey
 The file hosting the Xroot private key, needed to sign Xroot URLs.