UUID from specific Random seed value?

[matkatmusic]

PR here:

Uuids can now be created using user-supplied Random object

super simple fix: just move that Random to be an optional constructor argument.
Old:

//.h
Uuid(); 
//.cpp
Uuid::Uuid()
{
    Random r;

new:

//.h
Uuid(Random r = Random());
//.cpp
Uuid::Uuid()
{