Code cleaning and bug fixes

Some cleaning and fixes including:
- Cleaned up code for ContinuousLR factor which is not supported yet.
- Fixed the well-known Akka non-terminating bugs by try-catch in `DeepDive.run`
- Reduced test output by using --quiet in sampler
- Fixed a warning that happens for a clean `make build`
- Skipped chunking on GP to ensure `make test` work on GP
- Fixed some occasional testing bugs

See the commit messages for detail.
The difference between `lazy val` and `val` is, that a `val` is executed when it is defined, and a `lazy val` is executed when it is accessed the first time.

We had encountered some problems when executing DeepDive.run several times in integration tests. We have been using some hacks to fix it (running these tests one by one in separate `sbt` commands). If we can fix it, we can run all tests together.

I have to investigate more into the alternative. A possible way might be initializing `Context.system` explicitly every time `DeepDive.run` executes (not sure how), or making `Context` a class rather than an object. But I am not sure.