Attribute table data checks

Run checks on the input data to avoid issues with EnergyPlus simulation:

[x] Raise error if any of the basic attribute columns are missing
[x] Verify shading column are all true/false (either bool type or string)
[x] Check height exists for every polygon
[x] Raise error if UID value is missing
[x] For non-shading polygons, check that all the other fields have been filled out
[x] Raise error if zero height detected
[ ] Config file checks
[x] Check for duplicate UIDs

UCL / simstock_qgis