Simplestmaps

- Add support for multi polygons inside geojsons.

- No more _set helpers to work with element sets! (including internal refactor for readability)

- Added support for Telluric geo features and geo vectors out of the box!
- Fix: when converting sequences of coordinates, if the result is another type of object that needs
to be converted, keep converting them.
- Fix: suppport older versions of shapely in which geometries can't be imported from the root
package.
- Fix: custom coordinates sequence objects that evaluate to False when treated as booleans, should
still be converted.

- Added suppport for Shapely geometries out of the box!
- Fix: custom coordinates objects was broken for coordinates sequences in the "_set" helpers.

- Added feature to automatically convert custom types of objects to coordinates or sequences of
coordinates, with the function `auto_convert`.
- More docs about the auto conversion and map customization features.
- Some internal small refactors for code reuse and readability.

- Added support for element sets with the new helpers: marker_set, dot_set, label_set, html_set,
line_set, area_set and geojson_set.
- New and improved docs and examples.