fixes a const-correctness error.
Starts adding a class for DKW (double-slip-switch Marklin style).
Fixe sconst correctness in LookupXXXDetector.
Starts refactoring turnoutbase components.
Finishes impl for DKW.
Adds fixed and movable DKW.
Fixes out-of-variable-ID problem in DKW.
Fixes a bug in the signal route resetting logic that prevented a signalblock traversed in reverse direction from ever losing the route_set_ba bit.
Adds a test for (fixed) DKW.
Adds extensive test for movable DKW.