Needed: A troubleshooting section

[adswa]

Following datalad/datalad#4651 (comment).
This can fit right into the "How to get help section". It should entail:

• short overview of the different log levels
• how to trigger "debug" messages and how to interpret them (DataLad: -l/--log-level or env $DATALAD_LOG_LEVEL, git-annex: -v/--verbose, --debug/)
• how to enter a debugging session: -dbg

... what else?

[jbpoline]

One thing that often trips the naive me is the git-annex debugging, and knowing if this is a datalad, git-annex, or interaction pb. I know there is "wtf" and that already should help - is there an equivalent git-annex wtf (that would be run first ...) ?