SFM: use old avec implementation in PBA

to avoid copying in avec::set
Merge pull request #117 from Waldteufel/sfm-old-avec

SFM: use old avec implementation in PBA
MATH: Matrix SVD and QR implementation and test cases
MATH: Matrix SVD sorting of eigenvalues, more test cases
MATH: Added QR decomposition interface
MATH: Matrix SVD and QR updates
SFM: Removing already existing matrix tools