tmpfiles: implement user tmp files feature

Add new action script tmp-files.sh, which allows user to
add files that can be lost between checkpoint and restore to the dump.
User files are stored in .tar.gz archive.
Tar command does all the file paths and attributes related work.

Fixes #65

Signed-off-by: Svyatoslav Vlasov <svloyso@gmail.com>
Signed-off-by: Eugene Batalov <eabatalov89@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>