SFM: initial MVE style fixes to PBA
SFM: use C++ headers, remove `using' from PBA
SFM: remove some artifacts from PBA

(keep the interface intact for the moment, though)

* we don't want to build PBA as a standalone library
* we don't use the GPU part of PBA
UTIL: add AlignedAllocator
SFM: use AlignedAllocator for avec in PBA
SFM: specialize CameraT, Point2D, Point3D for float
SFM: specialize SparseBundleCPU, avec
SFM: remove PBA frontend, use SparseBundleCPU directly
Merge pull request #106 from Waldteufel/sfm-cleanup

SFM cleanup, part 1