UNOMI-622: provide automation support for migration

[jkevan]

new env variable is usable to start a migration automatically during unomi startup: unomi.autoMigrate=1.6.0

Also now the migration config file is reusing existing ENV variables to get ElasticSearch configuration, this ease the automation and configuration process. The ElasticSearch configuration is now reused from the one used by Unomi by default. Env variable like this ones: UNOMI_ELASTICSEARCH_ADDRESSES, UNOMI_ELASTICSEARCH_USERNAME, etc …