Batteries extensions

[AHaumer]

As mentioned in #3285 I've implemented some extensions to Batteries (based on #3285):
cells and stacks equipped with sensors
stacks built as Ns x Np matric of different cells
Thus, one is able to investigate the influence of a degraded cell on the bahviour of the whole stacks. as well as to design a battery management system.
For active cell balancing, the stack models have to get equipped additionally with appropriate actors.

[dietmarw]

wrong PR.

wrong PR

[casella]

I'll take care of this ASAP, I guess it will take some time to do a proper evaluation

[beutlich]

I resolved the pseudo merge conflicts and rebased the branch.

[claassistantio]

All committers have signed the CLA.

[christiankral]

I changed variable name p to power in 91702ff and c0ad183 to be in line with the usual naming convention of the Electrical domain.

@AHaumer I wonder if we shall also change the variable name losses to lossPower or LossPower to avoid an additional variable name for a loss term.

[AHaumer]

@christiankral you're right with losses vs. lossPower

[AHaumer]

@christiankral
followed your advice and renamed losses to lossPower
resolved the bug introduced by renaming p to power (we have to correct the conntection to the bus variable, too - no error message since new bus variable p is introduced)