DirPath renamed to Path
The interface updated to the new lemon interface
Make difference between the empty path and the path from one node
Builder interface have not been changed
// I wanted but there was not accordance about it
UPath is removed
It was a buggy implementation, it could not iterate on the
nodes in the right order
Right way to use undirected paths => path of edges in undirected graphs
The tests have been modified to the current implementation