Revise Firmware and objects using it

[cwhanse]

Edits to ProdCertification: Remove the array FirmwareVersions, add HardwareVersion, keep Firmware, add ChecksumAlgorithm to Firmware

Firmware:

• Checksum
• ChecksumAlgorithm
• FirmwareVersion

ProdCertfication:

• Firmware
• HardwareVersion

Repeat ProdCertification if a certification applies to several configurations.

Device:

• (something for AppliedDate, Firmware) as an array of tuples.