Update pdl protocol to use signed ID when sending.

[jmfee-usgs]

Currently protocol accepts ID about to be sent, support digital signature on ID about to be sent option to verify and/or require. Add option to require minimum version of protocol to send.

[Capprin]

We want an HMAC signature of the product ID using its toString representation. You will probably want to make a utility class to do this. Add sign and verify methods to ProductId to facilitate this.

[Capprin]

Note: The end goal is to create a new PDL protocol version that verifies ID's before checking whether product has already been processed.

[Capprin]

The HMAC signature will be added as a new product signature option, and will probably be enforced with a new minimum signature version option.