Module implementation:

* Add functions for handle directory listings;
* Add functions for calling *stat on directories or files;
* Add unit tests;
* Add integration tests for smbfs module.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Add auth dialog

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
VFS: Add function for search superblock by any condition via callback
smbfs: ask credentials per host, nor per URL

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Code refactoring: extract functions from another function

Extract from: sftpfs_cb_open()
To:
 * vfs_s_create_file_handler() and
 * vfs_s_open_file_post_action()

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
smbfs: implmentation of file-related functions. Code refactoring

Signed-off-by: Slava Zanko <slavazanko@gmail.com>