Fixed bug in @dynSeries/align method (occuring if the second dynSeries object has more observations than the first one).

Reverted buggy commit 5366dd5cb9f546809ff21a0bd23a2ac423aac6ce by Ferhat and added call to strtrim in @dynSeries/extract method to remove leading and trailing white spaces in variable names.

Fixed bug. The cell of strings varlist had wrong dimension (must be a column) if the code is executed with matlab.

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.