Overhaul pdz.py

[gatesphere]

• pdz.py properly handles .pda files now
• switched to ArgumentParser CLI
• option to list contents of a pdz file without extracting
• option to extract only certain files from a pdz file
• experimental option to reconstruct headers for extracted pd* files (possibly incorrect, use at your own risk)

[castholm]

Checked out the branch and tested the script briefly to verify that both listing files and extracting pdz files containing pda files worked. I believe the signature for pdv is incorrect but I'll fix that in a follow-up commit since the page documenting the format is also wrong.

Thanks!