New WKB codes and improvements in the perturbations code. Bumped to 0.12.0.

Organized all wkb codes in nc_hipert_wkb which are used internally by
NcHIPertAdiab and NcHIPertTwoFluids.

Fixed problem when compiling against a static glib.
Improved nc_data_cluster_ncount and fixed documentation typos.

Adapted nc_data_cluster_ncount for the case where there is no objects generated by resample.

Corrected documentation of the kinematical models (desceleration -> deceleration).
Merge branch 'master' of ssh://git.sv.gnu.org/srv/git/numcosmo
Merge branch 'master' of git.sv.gnu.org:/srv/git/numcosmo
Updated ChangeLog.