rectangular leaves since bmesh.

finished

 - Setting any of the branch lengths to 0.0 results in divide by zero. Min value for the length setting is now 0.000001
 - Preset export failed with the change to the way that vector properties were stored. Now we just store a slice copy of the vector in the export.

indentation edits and copy pyrimid from contrib (where I had made some edits), removed so this wont happen again.

* General Rule (for Ivygen and Sapling): If you need more code for declaring the layouts than for the props itself, something is wrong. ;-)
* if > elif

- Fixed the assignment of vertex groups for rectangular leaves. Fix thanks to pawel_xx
- Compressed the UI to make accessing the different parameters easier. Also, the tree is not rebuilt every time a new menu section is accessed.

Fixed a memory access issue on OSX due to getting bezier point's coordinates after a new point was added to the spline. This caused corruption of the tree model.

 - Added tracker and wiki URLs
 - Fixed usage of Matrix.Rotation

[[Split portion of a mixed commit.]]