Fix sorting of vj in route schedules

We were only comparing vj with their first stop_time defined. So with this case:
```
A    7h00
B    8h00   7h30      
C           8h00
```
And we actually want: 
```
A         7h00
B   7h30  8h00
C   8h00
```
isn't it easier to allocate directly the vector ?