Split run_empire in Empire.py into several functions

[chriska85]

Currently the full EMPIRE model setup and solution is handled in a single function run_empire in Empire.py. There are a number of ways to split it up into several more specialized functions which can be called from the main run_empire function. The advantage would firstly be improved code readability as it would be clearer which parts are sort of self-contained. Secondly, it would be possible to write unit tests for the individual functions which can be run in a continuous integration framework.

[martinhjel]

Agreed. The Blocks feature of Pyomo could be useful for this.