[IMP] social share: -adds hashtags to buttons in forum views (+code clean
up)
		    -Add plain_content to store a text version of post content.

This is necessary because the Facebook OpenGraph crawler that reads meta
tags in the head of the file needs plain text in the og:description
tag content. This is extracted (if it exists) in the layout view
of the website.
[IMP] social share: hashtag data attribute processing, commenting,
code clean up and OpenGraph tags

hashtag processing: hashtags passed as data attributes in template
are process by the widget when sharing on twitter; this allows you
to specify relevant hashtags on your share link/button

OpenGraph tags: Facebook sharing needs OpenGraph (og) tags to define
the title, image and summary of the page. The summary needs to be plain
text.