add_strided_block in matrix_base
reorganize sparse matrix multiply with csr format
including the unused and unfinished attempt at a rewrite of sigma_ab
Check to make sure rows of C’ contribute to sigma BEFORE computing the rows.
check whether Fmatrices are used before updating their contents.
Merge branch 'master' into dist-ras

# By Toru Shiozaki (12) and Shane Parker (1)
# Via Toru Shiozaki
* master:
  some std::transform calls have been replaced by std::for_each
  further stabilized
  cleanup
  better runtime error message
  BFGS is now performed on ZRotFile. Replaces amat->exp() with diagonalization-based logic to make sure that there is no error.
  Another fix with tag_ub_. Also comforts clang.
  Checks against MPI_TAG_UB at runtime. MPI_Interface::tag_ub_ is the value of MPI_TAG_UB.
  fixes #25. for now.
  fixed "make distclean"
  bug fix. Initial denominator should be symmetric (it is real)
  bug fix. Initial denominator should be symmetric (it is real)
  refactoring
  minor (unverified)