Allow specifying multiple transaction types on the command line.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Allow changing transaction types during upgrade.

The --txntype option, while useful, overrode the types of transactions
both on load and store.  While this was fine for some types of
transactions, like the git type, this prevented converting from one type
of hash transaction to another.  Add an option, --from-txntype, which
overrides the load transactions only on upgrade.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>