Refactor code for modularization

[heringerp]

Large rewrite to allow the modular introduction of new analyses into panacus without having to touch many components.

This is still work in progress

Tasks:

• Introduce data manager to handle graph data (allowing multiple analyses to reuse data)
• Add Analysis trait which each new analysis has to implement
• Create Analysis implementation for all existing subcommands
• Hide inner workings from analyses
• Add more tests
• Restructure html generation

[heringerp]

Hi @lucaparmigiani, you were working on some major changes as well right? It might be beneficial if you could push these before I start making this PR merge-able, since there will likely be a lot of conflicts. However, for this PR there is still a lot of work to be done, so no need to hurry, I just wanted to give you a quick heads-up.

Best regards,
Peter