blob function is slightly reorganized

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
small change:== -> ===

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
[vault] make blob dir if not yet created

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
unit test for blobs backup

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
[helpers] restoring also directory

also fix: updating directory itself on importing

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
[helpers] preserve original file info

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
[vault] blob uses same time as original

to avoid replacing of the original file while restoring. Potential
issue: change time for blobs with the same content (equal hashes) from
different locations

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>