new result-type: Doclist, which is a Nethtml.document list

For results of tagselect this may make sense.
Other functions then can take over the work on the results.

(Alternatively more functionality could be introdusced in the extraction section,
but thta would lead to unnecessary mess and complexity there. Better allowing
other functions to take over work on an extracted doclist.)
Warnings removed by removing unused datatypes and adding missing stuff.