add path finding functions

[iH0118]

find shortest path between nodes and stuff like that

[fyrbnd]

Gonna write this soon, did it before around a year ago.

[fyrbnd]

I'd like to go through the complicated functions with you before we write them but I'm too lazy to type it out so let's call or talk in person about it.

[iH0118]

just added following stuff to neo.h:

• path type

  typedef struct path path;
  
  struct path {
    uint length;
    uint* nodes;
  };

• shortestPath function prototype

  path shortestPath(graph g, uint from, uint to);

[fyrbnd]

working on the internal logic on my head at least. gonna solve it recursive, but don't know how to handle circles yet.