5+5 benchmark: saving the script in HDF5.
5+5 benchmark: save versions of triqs and cthyb.
5+5 benchmark: downsample G(\tau) before plotting
DRAFT: Legendre GF accumulation

Basically an adaptation of code from cthyb_matrix. Not tested yet.
New benchmark to check Legendre measurement.
Results collection did not actually happen in measure_g_legendre.
Test for the Legendre measurement.
Put Hilbert space tools into triqs::utility namespace. Hopefully it will
not cause too much havoc.
Improvements of imperative_operator

* Templated on ScalarType (type of matrix elements).
* imperative_operator::operator() may pass a number of extra arguments
to ScalarType::operator() when applied to a state. This feature is
useful with user-defined function-like scalar types.
* New method update_coeffs(Lambda L) applies functor L to all
coefficients.
Merge branch 'hilbert_space_tools' of github.com:TRIQS/cthyb into hilbert_space_tools