Add associations
Set to commentable
Add position to mx_foreign_key_relations
Move lock_version's position and add default value
Add models and migrations for common columns
Change MxCommonColumnSet to be commentable
Change polymorphic symbol to mx_commentable from comment_owner
Add models and migrations for taggable
Add table version
Set basic routes
Change polymorphic symobl to mx_taggable from mx_tag_owner
Fix invalid migrations
Use t.references for polymorphic
Add identifier to mx_table_lists
Add rotues for table versions
Simplize build new comment logic
Taggablize
Add user columns to mx_tables
Change indices of mx_taggings to be simply
Add change_summary to mx_table_versions