[WIP] Migrator v2

[or-shachar]

Suggested simplified version of migrator app that will allow external contributors to better understand the mechanism of migrator.

Right now - we have MigratorInput class that has many members that are instantiated as we instantiate the class which makes it very hard to track and change.

I've managed to identify several building blocks and created traits to describe them.

I think the next steps are:

• Agree on this structure
• Adjust our current solution to work with those traits, add tests / integration tests where it's possible.
• Read configuration from RunConfiguration and instantiate collaborators as needed.

Still probably missing solution for resources packages, and main_dependencies. Need to iterate over all the special writings we do at the end of migration

[natansil]

Sounds good to me.
I hope that once we implement this Felix or some other developer will be available for testing it,
because writing this without a real world repo to migrate is problematic.

btw, we are focusing on monorepos right?