Add interface how components interact with each other

[vitaliimelnychuk]

As discussed in the group meeting, there are two possible approaches.

Option 1. Develop own format for migrations; convert existing migrations wroten on Knex, Phinx, etc. into Crispy format; build internal components relying on Crispy format only. This approach will allow localizing a need for 3d party adapters to a single point - conversion of migration files. The downside is that we need to re-implement all the low-level mechanics of DB migrations.

Option 2. Develop a set of components on top of existing migrations and leveraging existing tool's binaries. This requires less overhead to migrate from existing migrations framework to Crispy, but creates maintenance overhead by supporting adapters in multiple junctions of the stack.

See the schema for both options:

We decided to go with the option 1 since it's easier to start with and has a more clear roadmap.

Originally posted by @xTNTx in #5 (comment)

Based on the discussion we had there, we need better docs for crispy Components and how they interact with each other