When merging resources, the non-empty string value takes precedence.

The API package should be minimal, and example implementations should
live in SDK when possible.

Fixing docstrings to match sphinx-compatible formatting.

using unittest-standard asserts to adhere to conventions.

switcihng from Any to object works helps pass linting and mypy
compatibility.

The precedent that exists is to name both the interface and the
implementation in the sdk the same. This avoids the generally
unhelpful "Default" prefix.

opentelemetry-python is standardizing on Google style docstrings. As such
resolving formatting that is inconsistent with the style guilde.

Removing init from the abstract Resource class: it does not need to be
part of the Resource API spec. Other Resource implementations may
consume other arguments as well.

the master branch now include isort configuration that forces one import per
line.