Fixes for empty point geometries and more

[volcan01010]

Summary

This merge request fixes crashes where items had empty point geometries. There are a few minor improvements as well.

Closes #57 and the requirement for .AGS files.

To test

Run the application:

• [x] Confirm logging messages appear from app logger for validation
• [x] Confirm logging messages appear from app logger for conversion
• [x] Confirm East West Railway file runs without crashing (takes under a minute on my machine)
• [x] Confirm nonsense.AGS can be validated

Run the tests:

• [x] Confirm SettingWithCopyWarning messages are gone

[ximenesuk]

There is still one tiny issue:

INFO | 2023-02-23 08:39:06,975 | app.checkers | Checking against BGS data validation: LOCA within Great Britain
/media/colin/Data/repos/AGS/AGS-Validator-external/.venv/lib/python3.11/site-packages/shapely/predicates.py:798: RuntimeWarning: invalid value encountered in intersects
  return lib.intersects(a, b, **kwargs)
INFO | 2023-02-23 08:39:23,194 | app.checkers | Checking against BGS data validation: LOCA_LOCX is not duplicate of other column

So there must still be a duff point in the East West Railway file somewhere. However, the tests pass and so I am going to merge this now and create an issue for this to be investigated. The checking of the East West Railway file finishes on my system quickly enough but I still get a crash due to the size on the JSON file, but that's not related to our code.