Added saving S/MIME public keys

app/src/main/java/eu/faircode/email/DaoCertificate.java

@@ -35,6 +35,10 @@ public interface DaoCertificate {
             " ORDER BY intermediate, email, subject")
     LiveData<List<EntityCertificate>> liveCertificates();
 
+    @Query("SELECT * FROM certificate" +
+            " WHERE id = :id")
+    EntityCertificate getCertificate(long id);
+
     @Query("SELECT * FROM certificate" +
             " WHERE fingerprint = :fingerprint" +
             " AND email = :email COLLATE NOCASE")