Added routine for testing if a string contains letter(s).
Fixed typo.
Added 'Y' or 'A' for yearly data in dynDate class.

Follwing expressions are equivalent:

a = dynDate('2009');
a = dynDate('2009y');
a = dynDate('2009a');
a = dynaDate(2009);
Added test for integer input (dynDate constructor with one numeric input).
Cosmetic change.
Fixed typo (useless space).
Added tests in dynDate constructor (when dynDate is called with two input arguments: time and frequency).
Fixed copy/paste typo in unitary test.
Added new interface to dynDate. The constructor accepts a character ('Y', 'A', 'Q', 'M' or 'W') as the second input to specify the frequency instead of an integer (1, 4, 12, or 52). The following expressions are equivalent:

a = dynDate([1945 3],4);
a = dynDate([1945 3],'Q');
Added unitary test.
Moved the commented first line, used to declare that the routine has unitary tests, after the declaration of the function, otherwise help is not displayed.
Fixed bug. Added missing case for calls to the dynSeries::lag method.
Cosmetic changes. Removed useless curly braces and deleted trailing white spaces.
Added missing semicolon and deleted trailing whitespaces.