Fixed storing and loading nulls and booleans in Redis

See #1311 

- [ ] Fix `LuaScriptBuilder` to use `HEXISTS` in case of `null` values instead of comparison.
- [x] Fix `LuaScriptBuilder` to cast booleans to 0 or 1 before using these in conditions.
@qiangxue do you think it's important to have these null-values for all columns per each row?