new type: Document_array; save-command: saves Document_array also.
get_document-function added (refactored out providently, because of Get_urls, which will be completed soon).
just indentation changed for command-function (because get_document was added)
save a document as well as all subdocuments, tzhat are linked to via href's
get_document_list implemented; Get_urls working.

Now it's possiuble to get and save a document and all href's linked documents, for example.
(Each saved as individual file, not with directory-hierarchy.