This is a double-edged sword though as blind panic recovery
can lead to consistency issues in program state.
In particular, halting imapsql update push due to panic can lead
to a deadlock in IMAP code.
Panic in MTA-STS cache maintenance routine can lead to degraded
security.
Now imapsql module does not handle authentication. (it was not doing it so well
anyway)
sql_table module was introduced and used in the default configuration as
a replacement for functionality that was implemented by imapsql before.
Parts of maddyctl code were rewritten to make it work transparently with
any IMAP backend or credentials store.
Closes#212.
