Allow multipoint geometries

Created by: Rikuoja

Describe the bug Currently, only point geometry layers (not multipoints) are supported

To Reproduce Steps to reproduce the behavior:

1. Add e.g. the Formal Sector School Location Lower Myanmar layer from https://geonode.themimu.info/geoserver/wfs
2. Select the layer in plugin and try to run
3. Get python error TypeError: MultiPoint geometry cannot be converted to a point. Only Point types are permitted.

Expected behavior The plugin should calculate the isochrone for each point in a multipoint geometry.