Optimise load profile with DHW

[wouterpeere]

Currently, the optimise load functions cannot work with a DHW demand. This is due to the fact that, when optimising, there has to be made a choice to prioritise either the DHW demand or the heating demand.

In the issue, the goal is to implement that check to either prioritise heating or DHW so that DHW can be included within these methodologies as well.

This can be implemented after #220