Part::FaceMaker::ConstructFromType() could return null pointer if
abstract class type is supplied.
Here, it is fixed by checking for null pointer in facemaker itself,
rather than in every place ConstructFromType is being used.
* split Dir into Dir+Length; added second Length
* support for parametric linked direction: to arbitrary edge, and to
normal
* options: reverse, symmetric
* second taper angle
* changed offset join mode for tapered extrusion on OCCT7
Move from float to double
Further suggestions for float -> double move
Moved Tools2D from float to double
More suggestions for float->double move from Gui subdirectory
Changes to FEM constraint visuals for float->double move
Suggested changes for float -> double move
Suggestions for Part module moving float -> double
