* Adds ability to map forums to categories and tags as well as ignore forums.
* Fixes regular expression for detecting attachments in posts.
* Handles "remote attachments" 😮 by inserting a link.
* Imports view counts for topics.
* Handles incorrect references of parent posts.
* Better handling of quotes.
* Finds a lot more attachments by trying to replace various Unicode characters in filenames.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
* Try multiple filenames and do lots of guessing when searching for attachments
* Unescape HTML in filenames and replace invalid characters in filenames
* Existing permalinks prevented resuming of import
* Prevent duplicate attachments in same post
