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

[Bob]

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

I liked this idea for RMS and figured I'd implement it for AMS and Showcase as well.

When converting a discussion thread to a Showcase Item, 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).