Fixed a non-terminating bug in sampler

When sampler throw PermissionDenied error, (+x not set), DeepDive will
not terminate. Fixed this issue.
Update sampler for Mac to support -q/--quert
Reduced test output by using -q in sampler
Fixed a test bug when there is NULL in inference result

When highest bucket has 0 incorrect values, it has a NULL in the result
table, which leads to a test failure since x / (x + NULL) = NULL.

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Fixed Akka non-terminating bugs

DeepDive have suffered from non-terminating bugs. These types of bugs
are because exceptions are thrown out of DeepDive.run, but the Akka
actor is not shut down. We have been trying to capture these bugs by
catching them everywhere and run a Context.shutdown, but the universal
solution is catching any type of exception and shut down the Akka actor
whenever an exception occurs.

Added a try-catch block in DeepDive.run, and shut down the system when
exceptions are thrown. This fixes config parsing failures and
unpredictable exceptions.
Fixed learning rates for tests

Used previous learning rate, which is 0.5
Merge branch 'hotfix-clean-continuousLR' of github.com:HazyResearch/deepdive into hotfix-clean-continuousLR