Combine create and edit post forms

[jbytes1027]

We have two forms, one for create post, one for edit post. One has a post preview, one doesn't. Both have a bit different spacing and width. The visual layer should be extracted to a component and reused.

[epadams]

I also want to mention that there's a lot of error checking in Create now but not Edit since the effort hasn't been duplicated to that component, we should try to do this sooner rather than later