uuid: Add module for UUID generation

This commit allow modules of afb-daemon to request UUID.

This introduce an abstraction above libuuid for 3 reasons:

 1. Using uuid had bad side effect inthe past because it
    required enought entropy at start time, leading to hanging
    initialisations in wait for enough entropy.

 2. Solving bug SPEC-2625 will require use of UUID.

 3. Porting to systems that haven't libuuid is made more
    easy after that.

Bug-AGL: SPEC-2625

Change-Id: I27d8b611946686dea6fab250697afe9b89aac869
Signed-off-by: José Bollo <jose.bollo@iot.bzh>