Invsearch

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**Features and Improvements**

**Minor Improvements**

**Bugfixes**

**Miscellaneous**

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**Features and Improvements**

- allow unhashable value in document. but fields with unhashable value are not indexed.
- add ``InvIndex.by_id(field=value)`` utility method. always assumes using one of primary_key field.
- add ``InvIndex.slow_find()`` method.
- use ``sentinels.NOTHING`` to distinguish not exists field from None value.

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- First release
- Implement inv search engine.
- Benchmark tested, beat in-memory sqlite.