list_comments api call improvements

• Improved sql for list_comments
• Removed materialized view from schema: it was not used, it required expensive refreshes
• Some calls are slow comparing to original hived calls
• by_cashout, by_update and by_author_update results are different than expected (waiting for merge from #47 (closed))
• fixed manual tests for list_comments
• Posting a comment will now update active but active is not propagating up at the moment,
• Added post object for database api post
• Added a possibility to convert amount notation to nai notation
• Other minor fixes

hive/db/db_state.py

@@ -346,7 +346,7 @@ class DbState:
             cls._set_ver(17)
 
         if cls._ver == 17:
-            cls.db().query("INSERT INTO hive_accounts (name, created_at) VALUES ('', '1990-01-01T00:00:00') ON CONFLICT (name) DO NOTHING")
+            cls.db().query("INSERT INTO hive_accounts (name, created_at) VALUES ('', '1970-01-01T00:00:00') ON CONFLICT (name) DO NOTHING")
             cls.db().query("INSERT INTO hive_permlink_data (permlink) VALUES ('') ON CONFLICT (permlink) DO NOTHING")
             cls.db().query("INSERT INTO hive_category_data (category) VALUES ('') ON CONFLICT (category) DO NOTHING")
             cls._set_ver(18)