Fixing figure caption

[MevenBertrand]

Currently the figure captions are of the form "Figure 3.1.:", which seems weird to me: why the point followed by a column? This PR removes that in the sidefigure and figure* environments, it might need adjustments for other kinds of floats as well. Please add a commit to this PR if this is the case!

[fmarotta]

Thanks! Having a dot after numbers is a German convention which I always disable by passing the numbers=noenddot option to kaobook, and I personally like the semicolon, but on the other hand I also see how it clashes with the dot (at the very least, this shouldn't be the default behaviour... my bad, sorry about that). Maybe a good compromise could be to choose the labelsep with an option, so that you could choose either "enddot + space" or "noenddot + semicolon". What do you think? :)

[MevenBertrand]

I agree, I like the semi-colon too! Your solution seems better than mine, I think in this case it might be a lack of documentation about the option noenddot option (at least I missed that solution). Probably adding a note somewhere on that, and maybe putting that option in the examples document might be enough? Otherwise indeed implementing my change as an option so that people who want to keep the German convention can is also a way to go.

[fredguth]

I guess this PR won't be merged. :-)