Add runscript for testing real option valuation for simple example

Code only valid for this special, simple example; the next step would be to implement a general function that can do the calculation for general cases. (Generalizations include e.g. more scenarios and specifying the year of the 1st stage decision, and the possibility to work with variations of the grid development plans depending on the strategy.) Also, no data files are included with this test implementation, so the script cannot yet be run to exemplify the calculations.

Closes #16 (closed)