web: why not use descriptive symbols for engines

[FormalMethod]

Currently, Project-OSRM-Web/WebContent/localization/OSRM.Locale.*.js references an ENGINE_0, and some l18n files mention ENGINE_1. Why not just use ENGINE_CAR_FASTEST, ENGINE_BIKE_SHORTEST, etc.?

[DennisSchiefer]

ENGINE_x simply references the ENGINE number x from the config file. As we do not know what engines users will come up with (e.g. ENGINE_CAR_SHORTEST_WITHOUT_USING_HIGHWAYS_THAT_HAVE_MORE_THAN_TWO_LANES_ALSO_AVOIDING_TOLLROADS), we left it intentionally generic.

[FormalMethod]

Then the localization should not be "Car (fastest)" but "Engine #1", don't you agree?