Agent/HostRandom::uniform<float/double>(min, max)

[Robadob]

The Random APIs only provide the range options for integer types, a user requested we add them for floating point types too. For consistency both host and device APIs should be updated.

Whilst looking into this, noticed the user guide doesn't have any details on our Random APIs. The only note about random is for initialisation, and gives an example using standard library random.

I might also rename AgentRandom to DeviceRandom for consistency with everything else whilst I'm at it.

Requested by a user here