Split SVDWorker.h/cc into spectrum.h and svdalgs.h/cc.
Implemented read and write methods for Vector and Matrix classes. (And just write for VectorRef and MatrixRef.)
Removed readVec and writeVec in favor of Vector::read and write methods.
Made former SVDWorker methods free-standing functions taking an optional Spectrum object argument.
Updated DMRG algorithm and DMRGObserver to use new Spectrum class for displaying eigs. Removed an extra template parameter from svd method which was causing a linker error.
Fixed linker error with csvd method. Updated unit tests.
Added comments describing each svdalgs.h template method.
Merge branch 'spectrum': removed SVDWorker in favor of free methods and
a new class Spectrum controlling truncation and storing density matrix eigs.
Changed implementation of IQTensor::conj() to conjugate blocks in place.