Detect if a file might be a maker archive
Ability to import an archive.

This also changes the name of the export function to archive_export
(to disambiguate with export).  Some utilities for inspecting archives
too, but none of them are exported.
Move archive export functions to free function.

Just to match import and to keep the main class easy to read.
Fix the simple interface

Now behaves more similarly to the full and the command line interface
with default targets.