Changes in XMBF 2.30:
---------------------

- added code for parallel bootstrap using MPI. To compile, use "make -f Makefile_mpi" (after adjusting
Makefile_mpi for your machine, if necessary). This generates an MPI executable called "XMBF_mpi",
with can be used as follows: "mpirun -np nprocs XMBF_mpi -b directory input.xml"
The number of bootstrap samples specified in the xml file must be divisible by the number of processes (nprocs).

- added an option for uncorrelated fits: <inversion_method> diagonal </inversion_method>

- four new "upper" matrix models for triangular matrix fits (= symmetrized matrix fits; see user manual for details):

  "multi_exp_mat_upper_model",
  "multi_exp_mat_II_upper_model",
  "multi_exp_expE_mat_upper_model",
  "multi_exp_expE_mat_II_upper_model"

- improved performance of the "chi_sqr_extra_term" option (compute derivatives only for relevant parameters)

- fixed missing space for standard output of fit results