Adds rake tasks for migration preparation
Adds adjuvant error messages
Supports non-interactive shell
Handles errors in rake tasks
Changelog.
Merge remote-tracking branch 'opf/feature/rails3' into migration/prepare_schema_migration_table

Conflicts:
	doc/CHANGELOG.md
Merge pull request #457 from opf/migration/prepare_schema_migration_table

 [MIGRATION] Prepare schema migration table