Added check that 'bifurcation' contains enough normals

In certain cases there are not enough bifurcation points exiting a
blanked group. This could happen when there are two centerlines where
one only has a very small deviation from the other. This does produced a
bifurcation group but there are no "exiting" points for the small
centerline.
Added check that all TargetSeedIds are found.
Explicit initialization for previousEdge2 variable and check on number of iterations

previousEdge2 variable was not initialized (caused Run-Time warning in
Visual Studio).
Added explicit initialization and helper variable for number of
iterations to only check previous edges after initial iteration.