Pass parameter to specify how long execute binary|hack should run for

At the moment execute python hack and execute binary on the client will be automatically killed if they take longer than a minute. We've worked around this by having a separate thread call Progress in the python hack itself, but this is a nasty solution.

The ExecuteBinary/PythonHack client actions should take a "timeout" parameter that specifies how long the action is expected to run for. We heartbeat that many seconds into the future.