Stretch support

- Support Debian Stretch (MariaDB debian/upstream + Galera)
- Doc updated
- New travis tests (with Vagrant)
- Drop support of mysql_innodb_additional_mem_pool_size
- Xtrabackup optionnal installation + package name updatable
- Fix many issues with replication (Ansible 2.3)
- Auto-retreive master IP address on tests
- MySQL tools per OS release

meta/main.yml

@@ -4,11 +4,12 @@ galaxy_info:
   description: Install and configure MySQL or MariaDB (Galera Cluster) or Percona server on Debian 
   company: 
   license: GPLv2
-  min_ansible_version: 2.0
+  min_ansible_version: 2.3
   platforms:
   - name: Debian
     versions:
     - jessie
+    - stretch
   galaxy_tags:
   - database
   - database:sql
@@ -20,5 +21,7 @@ galaxy_info:
   - debian
   - galera
   - cluster
+  - jessie
+  - stretch
 dependencies: []