Implement file-based data migration (migrate_in).
modified create table/schema bugs! add create view.
Merge remote-tracking branch 'origin/macan' into zjw
Fix create_database_core bug by auto user authentication; Implement migrate_stage1.
Implement migrate_stage2: remains file collection and targetFileMap.
Merge remote-tracking branch 'origin/zjw' into macan, bug fix for table/schema.