mod_client_management: Add support for revocation of clients (when possible) We decided to keep the unified listing of "clients", which includes both SASL2 clients and OAuth grants, etc. To a user, or someone wanting to manage what can access their account, they are largely equivalent. To accomplish this technically, we add a prefix to the id to state what type it really is.

This module logs events where more than a certain amount of CPU time was
spent.

``` lua
log_cpu_threshold = 0.01 -- in seconds, so this is 10 milliseconds
```

Uses the Lua
[`os.clock()`](http://www.lua.org/manual/5.2/manual.html#pdf-os.clock)
function to estimate CPU usage.