Introduce the concept of a DRC_PROVIDER which allows
to separate the various DRC functions to their own
areas. This allows, amongst other things, a slimmer core
DRC class, and allows DRC functions to be separately testable.
The courtyard DRCs (overlap, missing and malformed)
are the first victims, so instrumentation can be added to this function.
Add some unit tests on this DRC function, as well a few re-usable PCB-based
utility functions in a library (qa_pcbnew_utils) that could be shared between
unit tests and other utilities.
This includes:
* Linkage against the Boost unit test libs
* Configuration of the Boost libs
* A place for common generics "extras" for unit test harnesses
including
* A simple way to allow "expected-failure" tests (without
breaking Boost < 1.58, e.g. Ubuntu LTS)
* Moving some simple numeric predicates from the geom tests
to the utils library.
Expand unit test docs to describe the expected failures macro.
Add a few COLOR4D tests, including one with expected failures due
to a pre-existing bug. This will be fixed in a follow-up commit.