Extractor Append and Prepend replaces arch.
globals params set to kdiff3, with todo on WinMerge and ditto.
AddMatches() and Replace() memorizes regexp group.
ExtractorMatch.ExtractFrom() add match to prg.matches.
uses prg.Replace() to replace _Sarch_ and _S1_, _S2_, ...
Update p.archive is BuildZip() is called.
Referer can be replaced by url.
Add Exit point to GetArchive() and GetURL().