It does redirect to "/files" on success, so user doesn't even see the
strange "/create" URL at all.
This commit is for keeping these handlers small, not making one
(FilesPageHandler in this case) do everything.
Its handlers are now more compact. This commit moves Handler classes in
handlers\ directory.
ResourceHandler ignores "hidden" files in the archive, and these are
used as markup templates in IndexPageHandler and FilesPageHandler.
