Clean up version attributes

Rename mysql.version to percona.version to keep in our own namespace.
Use variable instead of hard-coded version in cluster recipe.
Update default version to 5.6
Merge branch 'mysql-dependency' into integration

* mysql-dependency:
  Clean up version attributes
  Remove dependency on mysql recipe
Merge branch 'cleanup-replication' into integration

* cleanup-replication:
  Simplify password usage for mysql client
  Cleanup for readability
  Split master and slave sql grant files