Add tools for releasing and shipping

[amotl]

Dear @jpmens and @linusg,

in order to bring this program to a wider audience, I suggest to spend some cycles on some rather boring topics.

Gradually, I would like to [see]:

• Improved release management. Add bump2version and switch to Semantic Versioning like mqttwarn is doing these days.

• Automatic package building. We should provide ready-to-go packages for popular operating systems on the GitHub release page. The OwnTracks clients for Android and iOS already do that, so let's try to fill this gap for Linux and FreeBSD. See #4.

I am starting this looking forward to a sensible discussion loosely around these topics and hope this resonates well with you.

With kind regards, Andreas.

[jpmens]

I have submitted ocli for review for inclusion into the OpenBSD ports collection.