* In the implementation for the *Traverse strategies the next method performs an unguarded list directory. If the directory is not accessible an unrecoverable error is raised thus ruining the walk. This changeset adopts and adapts the error handling protocol as defined in Python's os.walk function where errors from listdir are ignored or are reported to an optional on error callback function.
* Expand DirectoryIteratorsTest testsuite to confirm the hardened iterator behaviour over unreadable directories.
* Expand DirectoryIteratorsTest testsuite to confirm the hardened iterator behaviour over
unreadable directories. Correct bad formatting
* fix clang compile
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)
