Random seed in ALE cannot be set

[katja-hofmann]

The code in https://github.com/Microsoft/malmo/blob/63fbaad6501905a6667e393d4d6318a6107be7fe/Malmo/src/ALEAgentHost.cpp#L83 suggests that the same seed (123) is used on every run using the ALE environment. This should be set (a) to a different seed on each run, or (b) to a user-provided seed. Ideally, both should be possible.

[DaveyBiggers]

Have added ALEAgentHost::setSeed(int).
(Not ideal, since it breaks the whole keeping-the-agent-host-inferfaces-the-same paradigm, but then, that never made much sense anyway.)

Calling setSeed(123) will reproduce the previous behaviour, which was always setting the seed to 123.
Calling setSeed(0) will cause the ALE to seed from the current time each go.