New calculation in CheckExplorerPath leads to too long or too short routes

[César Benito]

New algorithm submitted in https://github.com/openrails/openrails/pull/270, which calculates train path using SNCA, leads to situations where path is too short (a few meters) or too long (more than 150 km):
Example of too long path: in Northeast corridor, the algorithm will try to clear all signals ahead with no limit. Tests show that this path is 200 km long, while taking into account SNCA should be of around 12 km.
Example of too short path: when starting driving, an EoA sometimes appears in front of the train due to a cause I haven't found. Path has to be extended in this situation.
Sometimes, OR crashes when resetting signals with Ctrl+Tab.