precondition check was being honored before, validating
if anonymous access is allowed on the metadata of an
object, leading to metadata disclosure of the following
headers.
```
Last-Modified
Etag
x-amz-version-id
Expires:
Cache-Control:
```
although the information presented is minimal in nature,
and of opaque nature. It still simply discloses that an
object by a specific name exists or not without even having
enough permissions.
Adds `-xver` which can be used with `-export` and `-combine` to attempt to combine files across versions if data is suspected to be the same. Overlapping data is compared.
Bonus: Make `inspect` accept wildcards.
