Auto-building remap operations & Coupled Sim Init

[jb-mackay]

Initializing a coupled simulation needs to be designed such that the actual remap operator construction can be hidden.

The init process might look something like:

1. Init all component simulations with existing standalone code
2. Init coupled simulation struct
3. Init maps using boundary spaces of each model
4. Reinit component simulations with updated coupled fields

[LenkaNovak]

To be addressed in #211