Implemented Set Prefix on Associated Thread during convert Thread to Article process

[Bob]

When a thread is converted to a AMS Article and the category settings define a thread prefix, then it would be nice if that prefix is automatically applied to the thread.

When converting a discussion thread to an AMS Article, if the "Add Prefix to Thread" option is set for the selected category, then the post convert process will include updating the discussion thread record and setting the prefix (regardless if there is an existing one set or not).