this += other now supports
other <= this

Internally lotaMemory=true is the default
prefix + NoSaveLanczosVectors=1
should be used to have Lanczos not save vectors

Concurrency::setAffinitiesDefault added to control
global setting.
Moreover, PthreadsNg class has a setAffinities(bool) member
to set affinites on a algorithm-by-algorithm basis
if needed.

if lotaMemory is set, now checks that memory allocation
succeeds, if it doesn't it degrades gracefully
to lotaMemory=false