Allow submitting topics with identity revealed

[cdnbacon]

Some people submitting topics want to be identified instead of submitting anonymously.

Deliver in two phases

1. Update instructions on topic form

Add your name at the end of your question if you want to be identified.

2. Update model to consider how identity of topic submitter is treated

1. Deliver UI affordance on topic form to update model
2. Represent if topic was submitted anonymously
3. Update topic display to show non-anonymous topic submitter as appropriate