Add regular expressions in @dynSeries/subsagn
We already have the possibility to use regular expressions in @dynSeries/subsref. The code should be factorized and reused in @dynSeries/subsagn. This would allow syntax like:
ts{GROWTH_GDP_@US,JP,FR,GB@} = ts{GDP_@US,JP,FR,GB@}.ygrowth
where ts is a dynSeries object.