JS Api: added an active_page variable to make it easier to denote the context from javascript
templates/post_thread.html: changed windows-type endlines to unix-type
templates/post_thread.html: add data-board field for every thread; mainly for post-hiding and ukko integration
post-hider.js: fixed multiple board issues; eg. you could hide a thread on one board, and threads from other boards with the same id would have been hidden too
post-hider.js: further code cleanup; fix displaying on board pages