Make post status more visible on Manage/Posts tab

[tellyworth]

It's often difficult or impossible to distinguish between different post status types on the Manage/Posts page.

This patch adds a new CSS class to each table row based on the post_status value: 'status-publish', 'status-draft', 'status-future', etc.

I haven't changed the admin CSS to take advantage of this; I'll leave that task for the design experts. Example CSS selectors below:

#the-list tr.status-future { /* future row */ }
#the-list tr.status-draft td { /* draft cell */ }
#the-list tr.status-publish th { /* published heading */ }

manage-post-status-class-r5797-a.patch is an alternate patch with an additional feature. As well as the status class, it applies a second class to indicate whether the owner of the post is the current user ('author-self') or someone else ('author-other').

(In [5799]) Add classes that indicate post status and author ownership. Props tellyworth. fixes #4628