n-dimensional space q-flat -- point orthogonal projection

[make-github-pseudonymous-again]

see :

• http://en.wikipedia.org/wiki/Flat_%28geometry%29
• https://en.wikipedia.org/wiki/Projection_%28linear_algebra%29#Orthogonal_projections

dependencies :

• js-equation #23

related :

• n-dimensional space line -- point orthogonal projection #24