mod_rest: Add mappings for a whole pile of XEPs Look ma, programming in JSON! XEP-0012: Last Activity XEP-0077: In-Band Registration XEP-0115: Entity Capabilities XEP-0153: vCard-Based Avatars XEP-0297: Stanza Forwarding XEP-0308: Last Message Correction XEP-0319: Last User Interaction in Presence XEP-0333: Chat Markers XEP-0367: Message Attaching XEP-0372: References XEP-0421: Anonymous unique occupant identifiers for MUCs XEP-0428: Fallback Indication XEP-0444: Message Reactions

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.