gpt: Support for GPT (GUID Partition Table) restoration

The restoration of GPT table (both primary and secondary) is now possible.
Function 'gpt_restore' presents example of partition restoration process.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Piotr Wilczek <p.wilczek@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>