Generic tests for algorithms implementation

[guimarqu]

When I tried to use the regular storage in #748, I experienced how painful the implementation of a new algorithm is. The first reason is obviously a lack of documentation, the second is that you need to run the algorithm to make sure that you implement the "API". To waste less time, it would be nice to have a generic integration test for algorithms that test the following methods:

• run!
• get_child_algorithm
• get_unit_usages
• make sure that we can access data stored in the unit storages used by the algorithm