Asqlcell

What's Changed
* Support label and legend switch by samuel-1184 in https://github.com/datarho/asqlcell/pull/19
* Combo chart by linbendatarho in https://github.com/datarho/asqlcell/pull/20
* Sunsurt chart by linbendatarho in https://github.com/datarho/asqlcell/pull/22
* Support some themes

**Full Changelog**: https://github.com/datarho/asqlcell/compare/0.2.0...v0.2.3

What's Changed
* Update dev environment by samuel-1184 in https://github.com/datarho/asqlcell/pull/12
* Magic extension improvement by samuel-1184 in https://github.com/datarho/asqlcell/pull/13
* Altair by linbendatarho in https://github.com/datarho/asqlcell/pull/15
* Use Python 3.8 by samuel-1184 in https://github.com/datarho/asqlcell/pull/18


**Full Changelog**: https://github.com/datarho/asqlcell/compare/v0.1.8...0.2.0

1. Visulization supported Pie chart, Bar chart, Line chart and Point chart.

2. Multi-series in one chart.

3. Conditional Format in Table.

4. Category scanning in header of table.

5. Improve performance.

6. Bug fixing.

1. Keep sql result set after saving and refreshing.
2. Allow to ommit dataframe variable name.
3. Improve performance.
4. Bug fixing.