Chang branch

-- Updating the "nav_to_coord", making it to be able to accept cancels of current goals (preempted).
-- Updating "say.py": the sleeper is removed (put in 0.1 seconds) because it is useless to sleep 3 seconds as the activation of the ASR is a blocking function, it will wait until the ASR is activated, so it is useless to have a sleeper.
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