[versit] Handle malformed concatentations of vCard files

If vCard documents which do not end in \r\n are concatenated together,
the result is a malformed vCard document with a line like
END:VCARDBEGIN:VCARD\r\n
in it.  This commit adds logic to the parser to detect those types of
lines and replace them with
END:VCARD\r\nBEGIN:VCARD\r\n
lines.

Signed-off-by: Chris Adams <chris.adams@jollamobile.com>
Change-Id: I9de0bfebaa640fd2a166342e4e310edb76f1cc15
Reviewed-by: Matthew Vogt <matthew.vogt@qinetic.com.au>
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Renato Araujo Oliveira Filho <renato.filho@canonical.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>