Non concurrent processing of files in LW FilePoller

LW FilePoller component always processes files concurrently. Sometimes it's very important that files get processed in a defined sequence, because the contents is depending on previously processed contents.

I've extended the LW FilePoller class. It has a 'concurrent' property now (default is true) and properties for sorting the incoming files (Sort by name and last modification date, asc and desc)

Maybe this functionality should be included in the LW FTP FilePoller and servicemix-file BC, too.