Add QGISWriter

[JakubCha]

• Adds QGISWriter to be used in case of qgis output. It creates QGSVectorLayer that's populated similarly to DataFrame. I had to make a few workarounds (static methods) to satisfy QGSVectorLayer demand of setting correct geometry and field types during feature writing.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.38%. Comparing base (e429cb8) to head (9d2133c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #99 +/- ## ========================================== - Coverage 91.49% 91.38% -0.11% ========================================== Files 85 78 -7 Lines 5736 5095 -641 Branches 577 577 ========================================== - Hits 5248 4656 -592 + Misses 455 406 -49 Partials 33 33 ```

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[dbaston]

@JakubCha this passes tests once rebased onto master. Are you OK with me merging it?

[JakubCha]

Yes! Thank you for helping implement this 🙌

[dbaston]

@JakubCha if you need wheels with this change they are available at https://test.pypi.org/project/exactextract/0.2.0.dev180/