layers depth should be explicitly passed to compass and validated

[alon-e]

currently, the depth is inferred by the layers folder structure. but if a file is missing or partial no error will be thrown.

also, when compass runs out of leaves it will fail on a non-informative error.

[GalRogozinski]

We have 2 issues: "when compass runs out of leaves it will fail on a non-informative error" - P2

Add a configuration for layer depth - P3