...as suggested by Bernd + Stefan

...also in this commit: Some minor cleanup

...this surely is not yet the final version.

The fixed bug was the ignoring of the ldaU XML element if the version number
of the inp.xml file was not 0.29. For the NiO_ldauXML test this meant that
no linear mixing was used for the density matrix.

Please note that there are still slight differences between the results
obtained with this version and the last release version. I changed the
reference value for the total energy from -3191.9717 to -3191.9707.

...there was a missing initialization if no cdn.hdf file was used.

Note: Also in this commit:

1. Changed test values in NiO_ldauXML test since now the broyden files get deleted
   when a new density matrix is generated
2. The NiO_ldau test should not work any more since linear mixing for the density
   matrix is removed for the old inp file. (It is not specified in the n_mmp_mat
   file any more)

...not yet used.

...it is not yet read in.

Note: Two changes have been done in global/types.F90:

   1. MERGE(jsp,4,l_noco) -> MERGE(4,jsp,l_noco)
      (I think the new code is correcter. This change is required)

   2. Some dimension variable was replaced by stars%ng2.
      (Maybe this is not required and maybe the previous variable was more correct.)

This commit introduces general LDA+U parameters (for mixing) to the inp.xml file.

For example one can now say
-xmlXPath /fleurInput/cell/bulkLattice/\@scale=1.01
to scale the systems lattice by 1%

...hope, it works.

The k point density can now be defined by specifying denX, denY, denZ
parameters in the &kpts line.

Fixes to make pbe faster (again after refactoring of xcpot) Changes for reanabling old CPP_66 functionality

-removing of variable icorr, use of member-functions instead
-removal of icorrkeys module
-removal of hybridmix module
-cleanup at several places