anchor.diff:  .Required Checks
   |===
   | ID | Check | Description
  -|      R-1 | missing image files | Check all image tags if the referenced
  -                                image files exist.
  -                                See <<MissingImageFilesChecker>>
  -| [BrokenCrossReferences] R-2 | broken internal links | Check all internal links from anchor-tags
  -                                (href="XYZ") if the link targets "XYZ" are defined.
  -                                See <<BrokenCrossReferencesChecker>>
  -| [MissingLocalResources] R-3  | missing local files, either other html-files, pdf's or similar.
  -                                See <<MissingLocalResourcesChecker>>
  -| [DuplicateLinkTargets] R-4 | duplicate link targets | Check all bookmark definitions
  -                               (... id="XYZ") wether the id's ("XYZ") are unique.
  -                               See <<DuplicateLinkTargetsChecker>>
  -| [MissingImgAltAttribute] | missing alt-attribute in image-tags.
  -                            See <<MissingImgAltAttributeChecker>>
  +| [MissingImageFiles]      R-1 | missing image files | Check all image tags if the referenced
  +                                  image files exist.
  +                                  See <<MissingImageFilesChecker>>
  +| [BrokenCrossReferences]  R-2 | broken internal links | Check all internal links from anchor-tags
  +                                  (href="XYZ") if the link targets "XYZ" are defined.
  +                                  See <<BrokenCrossReferencesChecker>>
  +| [MissingLocalResources]  R-3  | missing local files, either other html-files, pdf's or similar.
  +                                  See <<MissingLocalResourcesChecker>>
  +| [DuplicateLinkTargets]   R-4  | duplicate link targets | Check all bookmark definitions
  +                                  (... id="XYZ") whether the id's ("XYZ") are unique.
  +                                  See <<DuplicateLinkTargetsChecker>>
  +|                          R-5  | Malformed links | Check all links for syntactical correctness
  +| [MissingImgAltAttribute] R-6  | missing alt-attribute in image-tags.
  +                                  See <<MissingImgAltAttributeChecker>>
  +| [UnusedImages]           R-7  | check for files in image-directories that are not referenced by any
  +                                  of the HTML files in this _run_
   |===
   
   
  
positive.code: | link-target       | Either a location in the current document (identified by ->id), another document (identified by URI)
                          or another resource to view or download.
  | local resource    | local file, either other html files or other filetypes (e.g. pdf, docx)
  |===
  
  
  
negative.code: [[DuplicateLinkTargets]]
  Duplicate link targets:: Links can have multiple identical link-targets (several id attributes with the same name).
    See <<DuplicateLinkTargetsChecker>>.
  
  [[IllegalAnchors]]
  Illegal links:: The links (aka anchors or URIs) can contain illegal characters or violate HTML link syntax.
  
  [[BrokenExternalLinks]]
  Broken external links:: External links can be broken - due to myriads of reasons: misspelled, link-target currently offline,
  