should be easier to discover archive state

[mmckerns]

When coming across a saved archive, one of the difficult issues is that there isn't a clear indication of what the archive settings are. Essentially, it would be good to be able to detect archive.__archive__.state from a given archive that is saved to disk. If the wrong archive type is selected, attempts to read the archive often fails. However, even the correct archive type with different kwd settings than used to create the archive can fail in a more subtle way -- the archive will be created, but there won't be any registered keys (so the archive seems empty). The state should be saved somewhere along with the archive, so that when interrogated with some sort of "detection" function, the correct type and state of the archive can be determined.