Targeted version of Ubuntu (14) is outdated

[sporksmith]

The README gives instructions for Ubuntu 14 and notes that Ubuntu 16 definitely doesn't work.

Unfortunately Ubuntu 14 is past the end of standard support (Ubuntu releases).

The latest Shadow's instructions and continuous integration are targeting Ubuntu 18.

The Bitcoin plugin README does say to use v1.12.0 of Shadow, but points to the latest instructions for installing Shadow, which are a bit different for the newest Shadow and newest Ubuntu.

If we don't want to invest effort into bringing this plugin up to date right now, perhaps we could improve things by pointing to more specific instructions for installing the old version of Shadow?

[sporksmith]

Btw the wiki says that the newest supported Shadow is v1.10.2 (vs. v1.12.0 in the README). Presumably v1.12.0 is correct?

[robgjansen]

I think we initially made things work with v1.10.2, but I later did a small update for v1.12.0. So I think v1.12.0 is correct.

I don't think we want to spend effort on maintaining this plugin. Is it time to archive the repository as read-only to make it clear that we no longer support this plug-in? (Here is an example of how an archived repo looks.)

[sporksmith]

Archiving SGTM