remove pybol dependency

[orbeckst]

@ianmkenney said he doesn't want to maintain pybol anymore so we need to replace it with something simpler.

EDIT: ~Maybe this helps with the strange errors on CI, where templates cannot be found (eg PR #103).~ That was not pybol's fault and since moving to GH actions, none of these issues surfaced.

[orbeckst]

@ianmkenney can you please take a look together with @VOD555 ?

[orbeckst]

We can also add pybol code from https://github.com/ianmkenney/PyBOL into our tests (to get rid of one package dependency with unmaintained code) and then replace it eventually with simpler code.

[orbeckst]

In the meantime, we're updating pybol where necessary and wait for 0.3.0 https://github.com/ianmkenney/PyBOL/issues/25