Quote and Reply buttons for Posts

This pull request improves on my previous PR (adds #28) by allowing the user to choose between two quote methods depending on the goal.

Basically, there are two ways to quote someone:

* **Quote** button: appends the post content (with a bbcode [quote] tag) to the quickreply form at the bottom of the topic. Skips all other formatting by the original poster (only text, no layout/images/etc. leftover). Useful if you only need the text. This is handled entirely in Javascript with jQuery.

* **Reply** button: redirects to a form, pre-filled with the original post content, complete with all original formatting. Useful in case you really need to quote the original formatting as well. This is handled by the server.