WebComment: fix handling of links in comments
- Fixes the handling of URLs so that they do not disappear from the output.
- Detects links like: '<a href=" http://foo.com"> http://foo.com</a>' and tranforms them into '< http://foo.com>' (the link name is not necessary).
- Transforms automatically links into HTML context in HTMLWasher (http://foo.com to <a href="http://foo.com">)
- Adds 'automatic_link_transformation' param in "HTMLWasher.wash" in order to turn this feature on/off.
- Validates the possible links before making the transformation in order to transform just the valid links.
- Adds unit/regression tests. (closes #845)