Refactor Cliopatria loading and visualiser notebook

[edwardchalstrey1]

• Closes Update Cliopatria loading script to support 07052024 version #19
• Closes Move end years code generation to Cliopatria edwardchalstrey1/seshat#156
• Closes Handle colours for polity components better edwardchalstrey1/seshat#163
• Updates how to populate Videodata table by separating out the pre-processing step (including colour generation for each shape. This should be a bit easier to update from now on as the previous version of the populate_videodata script was a bit incomprehensible.

[kallewesterling]

Looking good - I just think we need to add some docstrings in, to make sure that we've future-proofed the code a little bit!

[MajidBenam]

All the changes seem good to me. I am enjoying (still learning) this new style of collaboration.

[kallewesterling]

Looks good to me!