Use twitter API's Tweet Entities for tweeted links

These changes substitute the original URL for the t.co replacement in tweets as they are added to the database table [enhanceTweet hook], this also means that the image extension starts working again with its code as-is.

For a tweet database with tweet entities and no substitution at insert the entities extension does the substitution at display time [displayTweet hook] {this is redundant if the substitution has already taken place [enhanceTweet hook]}.