Transfer metadata between objects based on geolocation

[vojtatom]

Allow transferring metadata between sets of objects based on geolocation.

• needs to be handled inside C++ since the metadata property is copied on transferring from C++ to Python

Expected implementation:

• Python API exposed on the level of Layers - target layer gets the source layer as a method parameter
• internally probably the best if it's implemented as a modifier (see modifiers.hpp) that accepts two vectors of objects - source objects (their metadata is being mapped) and target objects (their metadata is being enhanced)
• iterates through the source objects and if some geospatial condition is met (bounding boxes overlay?), the data is copied from the source object onto the target
• doesn't discard the original metadata in the target objects, overwrites are allowed only if the keys match

Possible inspiration:

• height-map based remesh operation
• height mapping