Make polymorphic comments, fix image controller

Make text comment  model and picture comment model
Delete comment controller
Make text comment controller and picture comment controller
Edit image controller def show
Put before_filter to image controller
Fix image model
Change comment partial
Fix image show comment
Make _textcomment and _picturecomment



this should be `render :new`
like all the others
unless there's a really good reason it has to be `:back` and only `:back`