Drag'n'drop of Sanger reads in the Project View

If there are two or more documents with chromatogram objects in the Project View, support the following feature:

• If a user drag one of the documents to another such document, the "De Novo Assemble Sanger Reads with CAP" should be opened with both files specified in "Reads".
• The same should happen for all child objects of such documents.
• If several documents have been selected, the list of files in the "Reads" field should contain all appropriate files.
• The CAP3 dialog shouldn't appear, if there is no Sanger data in the dragged item OR in the destination item.