Added primary key field to ConversationMessageRatings table (cnvMessageRatingID)

Added index to ConversationmessageRatings.cnvMessageID for potential join to ConversationMessages table and for where clause (cnvMessageID + cnvRatingTypeID)

Added index to ConversationMessageRatings.cnvRatingTypeID for potential join to ConversationRatingTypes table

Added index to ConversationMessageRatings.uID for potential join to users table