Parse constants.ini

[san-e]

I wasn't exactly sure where to put this, so I added the function to interface.py, let me know if you'd like it somewhere else

[biqqles]

Nice, you used paths.inis! I don't think it makes sense in interface.py, as you say, but need to think about it as the alternatives aren't great

• routines.py is kind of a dumping ground for random functions, but everything there constructs an EntitySet
• __init__.py might make sense but seems a bit weird to put a function there