key usage: added encipher options

Google Chrome 56.0.2924.87 on Linux Mint 18.2 reports
  [...]:ERROR:cert_verify_proc_nss.cc(942)] CERT_PKIXVerifyCert for music.hammerle.me failed err=-810
if flag 'encrypt' is not set.
> Key-Usage: sign,encrypt

gpgsm-params-template

@@ -1,7 +1,12 @@
 Key-Type: RSA
 # Key-Length: 2048
 Key-Grip: {subject-keygrip}
-Key-Usage: sign
+# X509v3 Key Usage: critical
+#   Digital Signature, Non Repudiation, Key Encipherment, Data Encipherment
+# Google Chrome 56.0.2924.87 on Linux Mint 18.2 reports
+#   [...]:ERROR:cert_verify_proc_nss.cc(942)] CERT_PKIXVerifyCert for music.hammerle.me failed err=-810
+# if flag 'encrypt' is not set.
+Key-Usage: sign,encrypt
 Serial: random
 Name-DN: CN=example.hammerle.me,C=AT
 Name-DNS: example.hammerle.me