Add fluentd configuration for MySQL error.log

- changed default logging to log file
- parametrized log file path
- added fluentd configuration
- introduced fluentd multi_format parser plugin

Currently error logs sent to syslog are represented
with severity ERROR, which is misleading for Notice
and Warning messages during service startup/shutdown.

Change-Id: I55106775fa54b412b50ecc10c12930445da15d03
Related-bug: PROD-21904 (PROD:21904)
diff --git a/README.rst b/README.rst
index 112a2db..b6be8e5 100644
--- a/README.rst
+++ b/README.rst
@@ -152,7 +152,9 @@
 - ``galera_xtrabackup_parallel``
    Default is 4
 - ``galera_error_log_enabled``
-   Default is ``false``
+   Default is ``true``
+- ``galera_error_log_path``
+   Default is ``/var/log/mysql/error.log``
 
 Usage:
 
@@ -166,6 +168,7 @@
       galera_wsrep_slave_threads: 8
       galera_xtrabackup_parallel: 2
       galera_error_log_enabled: true
+      galera_error_log_path: /var/log/mysql/error.log
 
 Usage
 =====