Feature: write shapefile fields to mesh attributes for access from Geometry/Shader Nodes

[SerLinkzero]

This PR add a feature to write attributes from shapefiles to mesh points, edges or faces, depending on the feature type.

This feature will allow access to the attributes from Geometry Nodes (with Named Attribute node) and Shader Nodes (with Attribute node), and facilitates data-based motion graphics and visualization.

Due to the limitation of mesh attribute data types, only float or integer fields will be written.

The PR also includes two utility options:

1. An option to allow converting dates to float values, in a format that the integer part indicates the year, and the fractional part indicates the ratio of the day in a year, e.g. 2023-06-30 will be converted to 2023.4958904109589041. This allow users to create time-based animation easier.
2. An option to map NULL to a user-specified no-data value. Since mesh attributes in Blender cannot be null, this allow users to specify an unlikely value in the dataset and remove features accordingly.

The attached video shows an example where the features are animated and stylized with a date field written to the faces.

2023-08-06.00-03-26.mp4