Add prefactorization in arap solver.
minivleft and minivright computes the left and right hand side
separately. arap.m is also updated to use minivleft and minivright
for speedup.
Add polar decomposition.
polar does the polar decomposition, and minir is rewritten by polar
decomposition.
Add a couple of skew functions.
skew, skewmatrix and skewvector have been tested by testskew.
Add polar derivatives.
dpolar computes the derivatives of R in polar decomposition.
testdpolar tests dpolar.