feature: deduplicate defaults and export defaults

[hbagdi]

With #419, programmable defaults are now supported.
State files are known to be verbose and repetitive since each and every field is exported.

Add a deduplicate mode in decK which only exports fields that are different from defaults and then export the default values as well.
This results in a much smaller state file with the same information.

[hbagdi]

#340 is another issue along the same lines.