Move depends.py core to the framework.

[mpg]

Similarly to what was done with all-core.sh, and analyze_outcomes.py, we want to split the currently monolithic depends.py script, which currently contains both code and data into:

• a core (python module that can be imported) that contains most of the code, that can be shared across branches, and should be moved to the framework;
• branch-specific executable script that imports the core and contains the branch-specific data (and possibly branch-specific code).

Depends on #97 - might be done at the same time, depending on the personal preference of who's doing it.