The syntax to get the number of observations and the number of
variables remains unaffected by this commit. If ts a @dseries object,
ts.nobs and ts.vobs are respectively the number of observations and
the number of variables.
The frequency and initial date can still be accessed with the usual syntax:
ts.freq
ts.init
It is also possible to get the last date:
ts.last
Added new methods frequency, firstdate and lastdate as alias for ts.dates.freq, ts.dates(1) and ts.dates(end)