Fixed error in the computation of the name of the google-test directory.
Option to deactivate building the MPS library
operator==() now returns Booleans; equal()/unequal() replace the old function that only returned a single boolean.
Added comparisons for indices. all_equal() is no longer a template, but a function. Added versions of the equal/unequal/operator==/!= for complexes.
Added all_equal() / some_unequal() specialization for sparse matrices.