**Rationale:**
Integral Types were missing and are needed for Project Nautilus.
**Changes:**
- Implements Integral Data Types
- u64 and i64 implemented through bigint
Reviewed-on: #13
Co-authored-by: Sergey Savelyev <sergeysav.nn@gmail.com>
Co-committed-by: Sergey Savelyev <sergeysav.nn@gmail.com>