Add Link rules to metadata.json in export archive

[CasperWA]

In order to:

• better help debugging export/import issues and
• keep information concerning how the archive was created,

I suggest we add a small dictionary to the archive's metadata.json file that simply states the rules used to generate the particular archive.
This may look something like:

{
  "link_rules": {
    "input_calc_forward": false,
    "input_calc_backward": true,
    "create_forward": true,
    "create_backward": true,
    "return_forward": true,
    "return_backward": false,
    "input_work_forward": false,
    "input_work_backward": true,
    "call_calc_forward": true,
    "call_calc_backward": false,
    "call_work_forward": true,
    "call_work_backward": false
  },
  // ...
}

[CasperWA]

Idea by @sphuber: If the goal is to have the best point from which to do debugging, one may consider to add the entities that are originally specified to be exported as well.

I agree, since the rules are somewhat meaningless without them. Indeed, one may consider to add all relevant user-changeable parameters.