Hard-code less capability types

[Viper007Bond]

We still hard-code some capability types thoughout the admin area.

For example edit_post is hard-coded as the edit attachment capability in the edit attachment pages. It should be pulled from the post type object instead so that it can be modified.

I've patched the ones I found.

'edit_post' is a meta capability. In other words, the conversion you made in your patch is already done in map_meta_cap(). Same for 'delete_post' etc.

Had we done meta capabilities with the rest of custom post types in 3.0, I don't think edit_post, read_post, or delete_post would have made it into the $cap object.