Added back the Toggle Post Details option to the Story Budget page

[raduconst]

This PR is a fix for #25
The Toggle Post Details button was removed here 95c6874#diff-9163f1310b94e41b397251a77e18ec5a but the setup_postadata is still not working so I couldn't use the the_excerpt function.

What I did instead is try to replicate the functionality that's used on the Dashboard → Pages area and take care of these three cases:

1. when the post is password protected, the There is no excerpt because this is a protected post. message is displayed (ref https://core.trac.wordpress.org/browser/tags/5.1.1/src/wp-includes/post-template.php#L400);
2. when there's an excerpt set by the user, display it (ref https://core.trac.wordpress.org/browser/tags/5.1.1/src/wp-includes/post-template.php#L412);
3. when there's no excerpt set, use wp_trim_words like explained here: https://developer.wordpress.org/reference/functions/get_the_excerpt/#comment-content-2457 Basically, this will generate automatically a text from the post content (ref. https://core.trac.wordpress.org/browser/tags/5.1.1/src/wp-includes/formatting.php#L3713).

I also made a little change on L474 and add the post-title class to the title column since the JS code that's adding the hidden class is still available.