Added functionality to post button

The post button now adds whatever it typed into the edit text next to it
to to the list of a picture's comments. These new comments are not sent
back to the list in the main menu, however, so the new comments will be
gone if the user leaves and comes back.
Added Functionality to Questions

The questions now display their answers when selected and the user can
post answers to questions or add their own questions using the post
button.