Give .wrap a max-width

[iammattthomas]

Let's make everyone happy here. Setting a max-width on .wrap at 960px, so now the page fits on a 800x600 screen, but doesn't get overly-wide on a high-res screen.

Changes to .submitbox necessary as a result, now floated instead of positioned absolute; new containing div around main Post page column to keep it from overlapping submitbox.

Also set a max-width and word-wrap on the .comment column on the Comments page; this keeps overly-long words from breaking layout (for the one browser that supports it currently, anyway).

[ryan]

(In [7101]) Set max width on .wrap. Props mt. fixes #6036

[ryan]

I added post-body to the edit page and link forms. Note that since the edit link form doesn't have a postarea for the editor, it doesn't have a min width constraint to prevent the submitbox from overlapping the left side when the browser is sized down.