Fix several bugs with handling e-mail files

- When converting from html->pdf, the wkhtmltopdf program exits with
  errors if the document contains invalid links. The content is now
  cleaned before handed to wkhtmltopdf.
- Update emil library which fixes a bug when reading mails without
  explicit transfer encoding (8bit)
- Add a info header to converted mails

build.sbt

@@ -295,6 +295,9 @@ val joex = project.in(file("modules/joex")).
       Dependencies.circe ++
       Dependencies.pureconfig ++
       Dependencies.emilTnef ++
+      Dependencies.emilMarkdown ++
+      Dependencies.emilJsoup ++
+      Dependencies.jsoup ++
       Dependencies.loggingApi ++
       Dependencies.logging.map(_ % Runtime),
     addCompilerPlugin(Dependencies.kindProjectorPlugin),