intermediate commit: including finite T lanczos calculation
-status: checking accumulation of requried states, almost done.
implement update of the number of required states per sector analyzing the list:
statistics of the list.

I noticed a possible bug in the Hamiltonian from local terms that
do not sum all the contribution to a given column j. check it out.
code written but still in a debug mode. many comments waiting to be reviewd.
- find a satisfactory way to separate the T=0 from the T!=0 case.
- use a unique list of states and find a way to determine and print ground state and possibly all the other state in a compact form
- use global variable for the ground state and partition function zeta
- add calculation of local Chi in the Lanczos algorithm
code tested for finite T Lanczos method:
- automatic setting of the number of states +nlanc_states kept in the list based on the criterium: exp(-beta(Ec-E0)) < \epsilon.
- T=0 and T!=0 in a single path in the code, +nlanc_states=1 or >1 chose among the two methods.
- single list for the states.
- added calculation of local Chi in the Lanczos algorithm. Some issues are possible for the
imaginary freq. domain. But the real-freq. and imaginary time compare perfectly and very good
resp. with fulled calculations.
TODO: one shot comparison with previous ED code.