Add script 'jitsi-auth-dovecot.sh'. Add/Justify some documentation.

conf/jitsi.conf.sample

@@ -19,3 +19,29 @@ FQHN_HOSTNAME=""
 # Defaults to: JITSI_REPOSITORY_VERSION="stable"
 #
 #JITSI_REPOSITORY_VERSION=""
+
+
+# DOVECOT_HOSTNAME
+#
+# Hostname of machine supporting Dovecot Auth Service
+#
+# Only needed if that type of authenticaten is provided
+#
+#DOVECOT_HOSTNAME=""
+
+
+# DOVECOT_AUTH_PORT
+#
+# Port on which Dovecot Auth Service is provided
+#
+# Defaults to: DOVECOT_AUTH_PORT=444444
+#
+#DOVECOT_AUTH_PORT=""
+
+# DOVECOT_AUTH_DOMAIN
+#
+# Domain agains authentication should work
+#
+# No default value
+#
+#DOVECOT_AUTH_DOMAIN=""