Add cider-log-show-frameworks command

[r0man]

This command renders the available log frameworks in a buffer. It shows the log framework name, the website and javadocs urls and the levels for now.

This is mostly to address @vemv's suggestion to ask the user to run (cider-sync-request:log-frameworks). I hooked the command up at the usual places and added it with a small troubleshooting section to the docs.

We could get even more sophisticated and show the current appenders and consumers but I need a user interface designer for this. Let's do this at some other point.

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[vemv]

Thanks a lot!

LGTM, but I cannot do a particularly deep dive atm.

btw, one thing that you might want to hammock is the behavior of selecting the sole available framework if there's only one.

Maybe we can keep the behavior but also (message "cider-log-mode: only one framework available, auto-selecting <framework>"). That way we leave something in the 'logs' so that things are less surprising when they go wrong.

Cheers - V

[bbatsov]

Thanks!