Flatten round configuration and consolidate related components

[aklenik]

Resolves #636

The PR includes:

• Converting caliper-flow to a class, and renaming it to CaliperEngine
• Flattening the round configuration syntax, and moving the processing to DefaultTest, which is renamed to RoundOrchestrator
• Move the round-related objects (monitor, report, etc.) to RoundOrchestrator, making CaliperEngine more lightweight (only flow control).
• Instead of the modules loading the configuration objects themselves from a file, they should receive the already loaded object. This will make the testing easier (no more fake YAML loader mocks).
• Instead of passing around configuration file paths, the modules could query them from the Config module (including the paths passed to the workers).
• Extract worker process message handling into a base class.

[aklenik]

@nklincoln These are the changes I plan in this PR. I'll add commits gradually, so it's easier to follow the changes (I'll squash at the end). Plus it's easier to run every test through the CI, hence the draft PR :)

[lgtm-com]

This pull request introduces 2 alerts when merging b82a3e4 into b6cf1eb - view on LGTM.com

new alerts:

• 2 for Unused variable, import, function or class

[aklenik]

@nklincoln The PR is ready for review. Let me know when it's time to squash

[nklincoln]

👌