New features:

* Add possibility to build a P(X,Y) model in two steps, i.e. a
  specific model for forecasting where a difference is made between
  internal links X-X or Y-Y and cross links X-Y.

  Ny is the number of variables Y out of Nv= NvX+NvY.

  k_XY is the target connectivity contribution of links X-X and Y-Y
  before switching to X-Y.

* Add new parameter links_selection for pre-selecting a short list of
  possible links to chose in for building the model.

* when the requested connectivity is attained, the couplings are
  output in file `couplings.dat'.

* New options -allcouplings added to output also
  the intermediary files.

Updates:

* Code optimization: due to code re-ordering and auto-vectorization by
  the compiler, execution is now 2.85 times faster on an example with
  2740 variables.

* better formatting and organization of the options in -h output.

Tag release 1.2