Math: generalize Gram-Schmidt algorithm for non-square matrices.
Math: don't needlessly include Matrix in GaussJordanTest.

Should save another bit of recompilation time in addition to previous
commit.
Math: Gauss-Jordan algorithm as pure functions.

No need to wrap this in a class.
Math: slightly faster Vector::projectedOntoNormalized().

The assertion will still compute the dot product (but not in release
builds).
Math: slight improvement of Gram-Schmidt orthonormalization algorithm.

Using Vector::projectOntoNormalized(), as it is slightly faster, renamed
the functions to properly mention that this is orthonormalization.
Math: added Gram-Schmidt orthogonalization algorithm.
Math: moved lerp() from Vector to Functions.h.

It does nothing special for vectors (unlike e.g. quaternion LERP) and
scalar overload is useful too.
Doc++
magnum-info: indent with 4, not 3 spaces.