Introduce 'vcard' option for the modules supporting vCards

The mapping between vCard's XML elements and YAML elements
of 'vcard' option is straightforward. For example, if you
want mod_muc to return the following vCard:
```
<vCard xmlns='vcard-temp'>
  <FN>Conferences</FN>
  <ADR>
    <WORK/>
    <STREET>Elm Street</STREET>
  </ADR>
</vCard>
```
you need to set the configuration as:
```
modules:
  ...
  mod_muc:
    vcard:
      fn: Conferences
      adr:
        -
          work: true
          street: Elm Street
  ...
```

0 files changed, 0 insertions, 0 deletions