refactor SWAP Params struct

[mortelli]

To be honest Params is poorly designed and was meant as an organizing thing for economic parametrization (thresholds, cashing strategy, amounts, etc.).

We have been refactoring the Swap constructor all the time recently, that is why instead of making a huuuuuge constructor with maaaany parameters (resulting in many changes), we started adding mixed parameters to this generic Params struct.

I would like to see a refactoring of this, but it does not need to be in this PR. Conceptually OverlayAddr does not belong to this struct, but LogPath neither does.

Originally posted by @holisticode in PR #1806