Simplify the EABContactFormatter API as follows:
* Drop all constructor arguments from eab_contact_formatter_new()
since get/set functions exist for all of them.
* Remove eab_contact_formatter_format_contact_async() since
EABContactFormatter does not block.
* Replace eab_contact_formatter_format_contact_sync() with
eab_contact_formatter_format_contact() which drops the CamelStream
and GCancellable arguments and takes a GString as an output buffer.
* Remove the "state" and "style" properties, and always use a white
background when rendering the full contact.
This is particularly important since render_normal() dereferenced
the GtkStyle without checking for NULL, which would crash on mails
with a vCard MIME part when "Show Full vCard" was clicked, because
the "vcard-inline" module never set a GtkStyle.
badc0e6156