Split de.evoal.core.main

de.evoal.core.main serves two purposes at the moment:

1. Provide base functions for all use cases
2. Implement the basics of the optimisation framework

We should split the module into two modules: de.evoal.core.main and de.evoal.plugins.optimisation. This would make the separation of these aspects clearer and remove optimisation-specific aspects from the core implementation.