Fix error logging.
rebranch to devel; fixed submodule; flatten commits on a branch
added restriction of URL scheme
Merge pull request #208 from IngvarJackal/htmlreader

Issue 138 (https://github.com/codingteam/horta-hell/issues/138)
Improve HtmlReaderPlugin logging and code cleanup.
Attempt to fix #210: use the server-reported encoding.