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- Fix bug: issue12, select statement with where syntax without priority
- SelectResult: `findall()` => `all()`, `findone()` => `one()`
- SelectResults: add `tuples()`, `dicts()`
- Removed `distinct()`, add keyword `distinct` (implemented as a type)
- Retrieving data way: inst; inst, func; func
- Add class `sql`, to declare a literal sql
- Lots of minor bugs fixed.