mod_http_oauth2: Reflect changes to defaults etc - Resource owner password grant was disabled by default - Tokens now include a hash of client_id making it possible to be reasonable sure that they were issued to a particular client

This module blocks configured queries that change server state.

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

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