Efficiency improvements. Rewrote some routines using regular expressions.
Fixed bug (month number 10 was missing).
Added new routine to test if a string can be interpreted as a date.
Added a routine for converting a string into a date structure.

A date structure has two fields:

 o freq, an integer scalar (=1, 4, 12, 52) specifying the frequency.

 o time, a 1*2 matrix of integers, time(1) is the year and time(2) the subperiod number.
Deactivated unitary test #4 in dynDates constructor.
Fixed unitary test #3 in dynDates constructor.
Changed dynDates constructor.
Rewrote @dynDates::eq method so that it handles correctly objects with only one element.
Replaced texinfo header by a plain text header.
Added routine to compare vectors of common length by lexicographical order.
Fixed typo.
Added dynDates::lt method. Overloads < opterator.
Removed @dynDate/lt method.
Added unitary test.
Added @dynDates/gt method to overload the > operator. Deleted @dynDate/gt method.
Only test the value of ndat member in @dynDates/isempty function.
Removed @dynDate/isempty.
Changed unitary test for @dynDates/eq (do not use the colon operator to instantiate the dynDates object). Added unitary test for the case where dynDates objects have only one element.
Changed @dynDates/subsref so that the selection of a single element in a dynDates object returns a dynDates object with one element (not a dynDate object).
Deactivated unitary tests #2 and #3 in @dynDates/subsref, changed unitary test #1 (do not use colon operator to instantiate a dynDates object) and added a new unitary test (to test the selection of one element in a dynDates object).