mod_rest: Roundtrip disco and items when string or boolean is used E.g. {disco:true} turns to <query/> and back to {disco:true}, same with {items:true}. Similarily, {disco:"node"}, {items:"node"} turn into <query node="node"/> and back.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```