Dealing with broken plugin and plugin needing extra setup

Nobody has claimed this yet.

While most plugin works out of the box, some plugins are either
- Broken: like Cryptocurrency/coin-alert.5s.sh relying on a no longer existing API
- Need extra setup: Some module require code modification or installation of additional cli tool, python module, etc... before working

For the Broken plugins, we can have two case:
- The plugin might just be deleted because it's very simple and if someone want the same functionality, it's no more work to start from scratch
- The plugin might have lots of functionality and good code (like coin-alert), so we want to keep it in case someone want to fix it, but we need to flag it. The goal of flagging it would be to avoid to display it in xbar GUI and having user complaining it's not working, while we already know that.

For the plugins with extra setup, we have multiple case:
- Some uses variable that need to changed directly in the code (API Key, etc..), we need to adjust them to use xbar variable system
- Some needs different kind of code modification like path ajustement to some cli tool, most of them probably need either code ajustement, better path detection and/or use of xbar variable system
- Some require to install a module or a cli tool to work. Some are already "good" but some just fail and need improvement to check for dependency and correctly report an error if something is missing.

That being said, I think we need a new metadata to tag the different cases, especially the non working one (to retain the code on github but hide in GUI) and the one needing improvement (usage of xbar variable, error reporting when dependency are missing, etc..)

Ideas for additional suggestion, a metadata name and metadata values are welcome..

Review the Cryptocurrency/coin-alert.5s.sh example and how plugin metadata is represented and consumed by the xbar GUI. Define metadata values that distinguish broken plugins from plugins needing setup or dependency fixes, then verify that the GUI can hide or identify them as intended.

Written by the indexing model from the issue text.