Remove nullable '?' for ContactsRequest.result attribute

The type is "any", which is already nullable as per:
http://www.w3.org/TR/WebIDL/#dfn-nullable-type
Transform ContactFindCB into a dictionary
ContactTelField should subclass ContactField, not "Contact Field"
ContactField.value attribute is no longer readonly
Fix example to use ContactTelField instead of contactField
Have Contact interface subclass ContactProperties
Add String enumerations for ContactFindOptions's FilterOp and SortOrder
Add enumeration for ContactsRequest.readyState
Define constructor for Contact interface

The constructor takes an optional ContactProperties in argument.
Drop [NoInterfaceObject] on ContactsRequest and have it subclass EventTarget