MAINLINE lib: uuid: add function to generate UUID version 4

MAINLINE lib: uuid: add function to generate UUID version 4

lib/uuid.c:
Add get_uuid_str() - this function returns 36 character hexadecimal ASCII
string representation of a 128-bit (16 octets) UUID (Universally Unique
Identifier) version 4 based on RFC4122, which is randomly generated.

Source: https://www.ietf.org/rfc/rfc4122.txt

Changes:
Move functions:
- disk/part_efi.c uuid_string() to lib/uuid.c -> uuid_bin_to_str()
- disk/part_efi.c string_uuid() to lib/uuid.c -> uuid_str_to_bin()

Update files:
- include/common.h
- disk/part_efi.c
- lib/Makefile

Change-Id: Ibedbbb4b4133d30dcc689bc4253e13370c9dc924
Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>