add a "reset date" function to scheduled posts

[jdingman]

SITUATION

You have a scheduled post, but you suddenly want to change it to post right NOW. There's no easy way to do that without editing the date, figuring out what day it is, what time is it, then modifying it all.

PROPOSED SOLUTION

Add a "reset date" button so it changes the information back to NOW and let's a user then click "publish" instead of "schedule", so the post is published immediately

[ryan]

See #8737