A few changes  1. Heisenberg model has been added, 2. btas library has been added 3. USE_BTAS flas is added to makefile to disable btas library
Merge branch 'master' of https://github.com/sanshar/Block
removed btas
added back only the required files in btas
Made some changes to btas so that the cblas class there dont conflict with our blas_calls.h. Maybe we should use the default clbas calls as well, but that is for future.
The first of a few uploads which will allow state specific excited state calculations to be performed. I think the code is more or less working, but this commit is meant as a first step where all the old functionalities are basically unchanged and the new ones will be introduced in the next commit
Now the state specific calculations with the restart option should be working. The normal statespecific calculations is sort of like a full restart, where all the wavefunctions are canonicalized and then a generate block is done and finally the normal dmrg targetting each state in turn is performed. The restart option is used when the normal state specific calculations fails at some stage. The restart flag first canonicalizes all the wavefunctions and then initializes the overlaps between wavefunctions. Finally it starts optimizing the last wavefunction it was working with and begins at the sweep iteration which it had previously died.
Small bug for non singlet state is fixed and the dmrg_test is updated
merge master branch