Refactor recipient access.

1) Refactor recipient class to support asynchronous loading operations.

2) Refactor recipient factory to simplify recipient access.

3) Consoliate everything into one recipient provider that is capable of
doing async lookups and intelligent caching.

src/org/thoughtcrime/securesms/database/SmsMigrator.java

@@ -128,7 +128,7 @@ public class SmsMigrator {
 
     try {
       if (sb.length() == 0) return null;
-      else                  return RecipientFactory.getRecipientsFromString(context, sb.toString());
+      else                  return RecipientFactory.getRecipientsFromString(context, sb.toString(), true);
     } catch (RecipientFormattingException rfe) {
       Log.w("SmsMigrator", rfe);
       return null;