This adds a few tests on:
* LIB_PART
* SCH_PIN
* SCH_SHEET
* SCH_SHEET_PATH
These tests exercise some of the basic code paths in these classes
and show some of the expected behaviours.
None of these tests are particularly ground-breaking, but they
provide a starting point to build out further tests, and to ensure
the already-covered behaviour is stable.
It does expose some places where SCH_SHEET could probably use const.
Redesignate the eagle test as eeschema tests and build
more like the other unit tests.
Enable as a test in Ctest now that the test executes without
crashing.
The loading of the file with the hardocded part is still
not enabled, as this needs more infrastructure to support it.