add a function in edge.java to determine if an edge has direction
add a function in edge.java to determine if an edge has direction

this can be sued to determine whether the edge needs to draw an arrow or not

Signed-off-by: Sam Phippen <e5a09176608998a68778e11d5021c871e8fae93c@googlemail.com>

samphippen/spe,samphippen/spe,samphippen/spe,samphippen/spe