This change does not add the pre-shared keys to the database but from
a security perspective this should not be done anyway.

If private keys exist the configuration is not overwritten so re-running
`genconfig` does not overwrite existing configuration.

TODO: add an option to generate new configuration (keys should be regularly
      rotated)

---

* pre-shared keys are recommended to help towards quantum resistance

  - https://www.wireguard.com/known-limitations/#post-quantum-secrecy

* this commit is based on:

  - k4yt3x#10

  (with the missing json import added)

add pre-shared key generation

* updates version number

* adds --psk / -p options to `wg-meshconf genconfig` to make the new
  functionality optional & disabled by default to not breaks existing
  user configuration.

* the new pre-shared key functionality does not store the generated keys
  as storing them in a spreadsheet alongside the private keys defeats the
  purpose. When using the new --psk option the keys are re-generated (as
  keys should be rotated periodically)

make new pre-shared key functionality optional

* fixes from the python 'black' formatting module

run black formatting module against the codebase

* as per the contributing guidelines

alphabetical imports

* upstream changes from:

  - master...k4yt3x:wg-meshconf:master

merge upstream

Revert "merge upstream"