Improve log management (#27)

* New log management (see #25)

- Add logrotate (as optional feature) setup
- Delete obsolete log management (log + log_slow_queries)

* Change log path

tests/group_vars/all

@@ -3,3 +3,4 @@ mysql_extra_configuration:
   innodb_commit_concurrency: 0
 mysql_use_percona_apt: true
 mysql_install_xtrabackup_package: true
+mysql_slow_query_log_enabled: true