Optimize Alpino call
Optimize Alpino call

Instead of calling alpino -treebank for every sentence (xml file), call it once for all files and then parse the results per sentence.
This reduces running time as the overhead cost of starting Alpino is pretty high, up to 50% for many short sentences.

cltl/morphosyntactic_parser_nl,cltl/morphosyntactic_parser_nl,vanatteveldt/morphosyntactic_parser_nl,vanatteveldt/morphosyntactic_parser_nl