New Spectrum Features; Fix IQIndexVal design
Miles, Srwhite59, Jessica Alfonsi, SDepenbrock, Lucas O. Wagner, G1257, Erik Schnetter, jgukelberger · Zenodo (CERN European Organization for Nuclear Research) · 2014
Added new features to Spectrum class: more complete interface for accessing eigenvalues and quantum numbers; ability to construct from diagonal tensors. Fixed design flaw in class IQIndexVal: was previously subclass of IQIndex which caused unexpected behavior when constructing ITensors from IQIndexVals. Now IQIndexVal holds an IQIndex as a data member instead. Minor updates to tutorial code. Fixed compilation error when using C++98 boost Foreach caused by some debugging code.