Add name option to make_BlockGf*

  modified:   pytriqs/gf/local/imfreq.pxd
  modified:   pytriqs/gf/local/imfreq.pyx
  modified:   pytriqs/gf/local/imtime.pxd
  modified:   pytriqs/gf/local/imtime.pyx
  modified:   pytriqs/gf/local/legendre.pxd
  modified:   pytriqs/gf/local/legendre.pyx
  modified:   pytriqs/gf/local/refreq.pxd
  modified:   pytriqs/gf/local/refreq.pyx
  modified:   pytriqs/gf/local/retime.pxd
  modified:   pytriqs/gf/local/retime.pyx