Add support for SIP addresses

Store SIP addresses of data kind CommonDataKinds.SipAddress
(called "sip_address" in the edit schema) as sip/sips URI's in TEL properties.
"sip" is added to URI's without scheme. Android allows a maximum of one SIP address for each vcard.

Requires update of ical4j-vcard to allow Telepone properties containing a URI: [ical4j-vcard-telephone-uri-mikma.diff](https://gist.github.com/mikma/7473048)