Make it possible to have a narrowed hemicycle

[RichardMN]

I've done an initial PR #60 which gives code to make symmetrical "hemicycle"-like parliaments which are less than 180 degrees. This gives a 1/3 circle range option, but it should be possible to prepare others, or even come up with a generic way of specifying this fraction (to enable, for example, 2/5).
This code (well, a slightly earlier version) has been used to make http://projects.martin-nielsen.ca/OneFortyOne/LTU-2024-Parliament-Results.html#interim-results

[zmeers]

Thanks Richard - will take a look at your PR now!