Database wrangler automation adapted to new scripts structure

Moved migration script to bin and separated Database Wrangler scripts into scripts folder. Updated failover.md with coded steps and added script paths. Added password for replication connection into source_vars_template.sh To run script through menu use follow command:

./migration (production|staging) database_wrangler

Script migration can be used by other roles by implementing a file steps_<role> using steps_database_wrangler as a template.