add missing unique indexes from migrations

db/migrate/20160125120915_create_learning_objects.rb

db/migrate/20160125121603_create_topics.rb

db/migrate/20160125124508_create_complaints.rb

db/migrate/20160125132447_create_bookmarks.rb

db/migrate/20160128123028_create_review_ratings.rb

db/migrate/20160130191533_create_topic_relationships.rb

db/migrate/20160217111317_create_rates.rb

...igrate/20160222102900_create_code_column_for_languages.rb

db/migrate/20160222144157_create_scores.rb

db/migrate/20160222144216_create_user_categories.rb

db/migrate/20160222144259_create_score_user_categories.rb