Better UX handling on identity key mismatches.

1) Migrate from GSON to Jackson everywhere.

2) Add support for storing identity key conflicts on message rows.

3) Add limited support for surfacing identity key conflicts in UI.

src/org/thoughtcrime/securesms/ApplicationContext.java

@@ -72,9 +72,7 @@ public class ApplicationContext extends Application implements DependencyInjecto
     return jobManager;
   }
 
-
   private void initializeRandomNumberFix() {
-    Security.insertProviderAt(new org.spongycastle.jce.provider.BouncyCastleProvider(), 1);
     PRNGFixes.apply();
   }