aleix's sandbox: Linkback semantic

This module is inspired by https://indieweb.org/Semantic_Linkbacks and will do these things:
Creates a new field called semantic type in linkback entity. If the linkback has fetched some metainfo and has some microformats semantics such as:
'in-reply-to'
'like-of'
'repost-of'
'bookmark-of'
'tag-of'
Will include it in the new field semantic type. This way you can create views grouping by semantic type.

Also provides a block with semantic linkbacks statistics for each content. And optionally a list of linkbacks grouped by semantic type if you don't want to create a new view.