Bunch of cosmetic changes

Closes #407

doc: dynDate: remove documentation about empty date (functionality in code to be removed at a later date).

Need to implement the test on 0/0 generalized eigenvalues later...

The option is passed in the fourth input argument of mjdgges. If the
mex is called with less than four arguments, then the threshold level
takes its previous (hardcoded) default value: 1e-6.

1 commit

Documentation, bugfixing, and cosmetic changes of recursive forecasts 

Closes #303

Make sure that recursive forecasting happens in increasing order of observations (required for plotting)