Throw an exception when no connection has been defined for a database (fixes #620)
Merge pull request #622 from K-Phoen/issue-620

Throw an exception when no connection has been defined for a database (fixes #620)
[migrations] add parameters to skip excluded or removed table from migration
[migrations] add optional comment for migration
Merge pull request #582 from jaugustin/migrations-exclude-tables

Migrations : skip excluded or removed tables