Fix type of ProfSampleCostCentre.profCapSet event field

[TeofilC]

This is a CapNo rather than a CapSet. The event stores this as an Int32, but CapNo is an Int16. So we need to do some conversions.

Resolves #84

NB: this is a breaking change, as we change the type and name of this field

[Mikolaj]

Maybe a sentence in the changelog? It's not entirely defunct, it seems.

[TeofilC]

I've added a changelog entry now

[Mikolaj]

Merged. Thank you, @TeofilC!