Render (some) HTML in the 'description' field

[twagoo]

1. Detect HTML tags in description and
2. Use a library to trim the markup down to a safe set of elements and attributes, stripping all remaining tags.

We probably only want to keep <p>, <a href="">,<br />, and possibly some basic formatting ones like <b>,<i> and <em> but no other attributes. We should also remove non-URL content in @href.

[kreetrapper]

maybe also <ul>, <ol> could be considered.