#388 Add option to restart dynamic pricing period

@drdla Please review. And are needed to minify post_edit.styl and laterpay-post-edit.js
post_id= is invalid HTML. Data attributes are how to do it right.
-> ```data="<?php ... ?>"```or ```data-post-id="<?php ... ?>"``` if you really want to have "post-id" in there as well.