Change all of the uses of std::pair<int, int> to be sf:vector2<int>

[gyurgyma]

To standardize with vector3 we should use vector2. The main change here is to turn all of the IntPairs in PathFinder::pathFind to vector2.

Also, maybe look into using float as our returned distance values for pathFind. This may help significantly for accuracy. This will decrease performance slightly, so make sure that it's fully tested and does in fact increase accuracy by a noticeable margin.

[gyurgyma]

nlohmann/json#486

[gyurgyma]

Tabling for now. Can't handle this VS compiler bug.

[gyurgyma]

Updated this to: Change all instances of IntPair and pair<T,T> to be Point2D/3D