added ListMap

ListMap is a map that does not order elements; used in
NameValueCollection to prevent reordering of message headers
multimap-like functionality
RecursiveDirectoryIterator and ListMap

1) Recursive and SortedDirectoryIterator

- added to VS projects
- fixed some style/formatting
- fxed windows tests

2) Added ListMap

Poco::ListMap is a std::mulitimap-like container that preserves
insertion order (needed to prevent Net message headers)