Glyph source bugfix 

This is a bug fix for a problem with assigning multi-dim arrays to the individual components of the vector data. 
This is because MGlyphSource stores an additional Nx3 array with the vector data and the update handlers were expecting 1-D arrays for the individual vector components. In the process of testing, fixed another inconsistency with the way scalars are treated. 

Note : I am assuming that the original intent is as follows : x,y,z,u,v,w,scalars are all allowed to be multi-dim, while points, vectors are supposed to be 2-d arrays (Nx3). Please correct me if this is not the case.