Add stochastiticity to clearing

[kim-mskw]

Curretnly there is the problem that when we have over capacity and multiple identical power plants bid the same, always the first x needed power plants get rewarded. This is just weird and should be fixed.

For example here pp_7 to 15 bid identical:

[kim-mskw]

Before clearing the orders should simply be shuffeld before they are sorted again.

[kim-mskw]

It does the trick