Fix the image_url_hack_insert/extract() to be a full message abstraction, or make imageurl an actual schema member #90

The database schema for message does not contain imageurl.

That functionality was added later such that in the code, we rely on there being a $msg['imageurl'].

However, it is only a run time construct; it does not exist in the database. The code, however, wants to see it, so often (but not always) after retrieving a message from the code base, it looks for <center><img src=..></center> in the message body and assumes it is a urlimg (image_url_hack_extract()).

Then, just before a message is written to the db, img_url_hack_insert() converts $msg['imageurl'] to a prepended <center><img src=></center> in the message body.

They are intended to be paired so we do not have to add it to the schema. However, they are not always paired. Create a MessageObject of some type that abstracts this away entirely.

Alternately, just make imageurl an actual db object instead of the current hack in message body.