Use the cpio headers instead of the rpm headers when unpacking.

The files in the cpio payload doesn't actually follow the file order
in the rpm headers, so we need to decode the cpio header and use the
information there.

Make transaction resolve step optional.

Don't add package to transaction more than once.

Mark package to be installed or removed after creating the transaction.

This lets us implement support for fnmatch wildcard and do
better error checking.

Detect failure to create download target file.

Create rpms dir on demand.

Silly spelling error.

Handle http errors better.

Handle arch correctly in command_download() and print some status at the end.

Remove redundant curl initialization.