Support single word rule composition

Today Duckling doesn't allow to create multiple patterns to match against a single word.
As a result, we can't compose rules/dimensions and have to duplicate the regexes.

This is the case for DE (e.g. [here](https://github.com/facebook/duckling/blob/master/Duckling/Numeral/DE/Rules.hs#L105) and [here](https://github.com/facebook/duckling/blob/master/Duckling/Numeral/DE/Rules.hs#L323)), NL (e.g. [here](https://github.com/facebook/duckling/blob/master/Duckling/Numeral/NL/Rules.hs#L104)), EL (e.g. [here](https://github.com/facebook/duckling/blob/master/Duckling/Duration/EL/Rules.hs#L121)), and RU (e.g. [here](https://github.com/facebook/duckling/blob/master/Duckling/Duration/RU/Rules.hs#L48)).