Add upgrade script 'upgrade-mattermost.sh'.

conf/mattermost.conf.sample

@@ -30,6 +30,18 @@ FQHN_HOSTNAME=""
 #MATTERMOST_GROUP=""
 
 
+# MATTERMOST_BASE_INSTALL_PATH
+#
+# The install cwpathdirectory is everything before the first occurrence of 
+# the string /mattermost. In this example, the {install-path} is /opt. If 
+# that command does not produce any results because your version is older, 
+# try whereis platform instead.
+#
+# Defaults to: MATTERMOST_BASE_INSTALL_PATH="/opt"
+#
+#MATTERMOST_BASE_INSTALL_PATH="/opt"
+
+
 # MYSQL_CREDENTIAL_ARGS
 #
 # Giving password on command line is insecure an sind mysql 5.5