BDirectory::Contains() is broken for certain cases of similar paths

[anevilyak]

Steps to reproduce:

1. Create a directory called New Folder.
   
2. Create a directory called New Folder 2.
   
3. Get a BDirectory object for New Folder, a BEntry for New Folder 2, and call BDirectory::Contains() on the resulting entry. It will (incorrectly) return true, because Contains currently compares the paths of the two up to the length of the directory itself. Attached please find a patch intended to fix the situation by comparing the path components individually.