Use global config

[ZzEeKkAa]

Use global config and remove json reads from the code. After these changes applied there should be minimal changes to add support for npbench.

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[diptorupd]

@ZzEeKkAa we need a better name for dpbench.config.C. How about default_configs?

[diptorupd]

@ZzEeKkAa Overall good progress. Few general comments:

1. I am not a huge fan of having lots of functions defined in __init__.py. Can you refactor and move the functions in dpbench.config.__init__.py into another module.
2. The functions currently in dpbench.config.__init__.py should have proper docstrings (use https://google.github.io/styleguide/pyguide.html#383-functions-and-methods as reference). We will then generate sphinx docs out of these docstrings as a "how-to" guide for external frameworks and benchmarks to be run using dpbench.
3. We have an embarrassingly non-existent documentation site. Let us start by adding a rst page on how the dpbench.config module should be used to create 3rd-party frameworks for dpbench benchmarks, provide architecture-specific configs to run benchmarks, and even load external benchmarks.

[ZzEeKkAa]

@ZzEeKkAa we need a better name for dpbench.config.C. How about default_configs?

I would go with dpbench.config.GLOBAL to avoid double config in the name.