Makes Finder::in() throw a DirectoryNotFoundException instead of an InvalidArgumentException if one of the directories is not found.
This behavior is more consistent with the AccessDeniedException for files which are unreadable due to insufficient permissions.
To keep BC, the new exception class inherits from InvalidArgumentException.
This exception is thrown when trying to open a non-readable directory.
Squashed commits:
[Finder] Fixed small errors
[Finder] small changes about AccessDeniedException
[Finder] removed unnecessary comment
[Finder] added access denied exception test
[Finder] Updated AccessDeniedException base class
[Finder] fixed access denied exception test
[Finder] native adapters now throw AccessDeniedException on stderr
