Resolve "Add an input block to define the systems to run"
New input block
Systems to define a list of systems to run.
It is now possible to have more than one system, although there are still not interactions between them. The different systems are stored in a linked list of polymorphic objects, so that it can store different types of systems.
- I have checked that my code follows the Octopus coding standards
- I have added tests for all the new features added in this request.
Closes #191 (closed)