SetupRHSforTDCSandTMS as well as fix for mapping field data 

SetupRHSforTDCSandTMS obtains electrode values now with loops. A check makes sure the data is not sent out of order, otherwise an algorithm processing exception gets thrown.

The mapping field data now returns the input as the output when the data is on the respective nodes or elements.
You can initialize a vector to 7 0s via the constructor:
```
std::vector<double> compare(7, 0);
```
and then kill the loop.