Rewrote tests with bats

As evidenced by the 11 prior commits, proper testing has revealed a
large number of gaps and inconsistencies in these scripts. bats is a
very capable replacement for the old test suite.

Big archival update

mktar now experimentally supports SHA256 checksums and age encryption.

mktar-batch is a version of mktar that strips out the 'clever' algorithm
detection and includes a batch processing/common passphrase mechanism.

Updated tests for mktar.

Remove temp test files

Remove static test files