Changed Today button to Now button for datetime fields.

Turns out that our clients want a Datetime for `publishedDate` and a `Now` button (which sets the date as well as the time) make much more sense.

EDIT: I did found a minor bug, not sure yet about the best way to handle this. Because it is JS, it inserts the date with the user's time-zone, but then on the Server it doesn't seem to convert it correctly.
So in my case, I am in `GMT+0100 (BST)` and the Server is in `GMT+0000 (UTC)`.

So in the frontend the timestamp would be `Thu Aug 14 2014 13:32:23 GMT+0100 (BST)`
and in the backend `Thu Aug 14 2014 12:32:23 GMT+0000 (UTC)`.
But currently it just seems to get saved as `Thu Aug 14 2014 13:32:23 GMT+0000 (UTC)`