make current sketch constraint work on 3d sketches better

[cekuhnen]

constraint like end point to end point works.

making a spline handle tangent / parellel to a line that is rotated in space is not.

https://drive.google.com/file/d/0Byzv_NlyKp_2cVVRaW9jOV9UVXc/edit?usp=sharing

you also notice some other funny bugs happening but those are reported already.

[colin.smith]

Adding to advanced modeling list