Feature/geojson

[KS-HTK]

• added more functionality to the geojson export function.

• updated some example networks to include a name, this can be usfull for testing.

• added a converter to convert the geodata in a network to geojson format and store it in a geo column in the bus and line table (according to comment of @ascheidl in #709)

• added a warning if the geodata is not in geojson format

• added a geo.rst for documeting plotting functionalty

• updated simple-plot.py to use geojson

• updated dump_to_geojson to use geojson in networks instead of geodata

• updated changelog.rst

Closes #2140 , #709