Removed Walk method from FileExplorer
Removed Walk method from FileExplorer

Now, file explorer have a compact interface capable of implementing all
reading operations.

FileFinder provide a better interface to search for files (instead of
listing directories every time). FileFinder is optional.

File type is used to group basic information about a File/Dir. Stat is
now composed by File

andrebq/exp,andrebq/exp,andrebq/exp