Reinstate `Geometry` module.
Fix compilation issues.
Minor reformatting.
Fix linking problems.
Merge branch 'develop' into maint-test-geometry
Merge branch 'develop' into maint-test-geometry
Rename test files.
Disable test of Sutherland-Hodgman polygon clipping.

It must be independent of the `Graphics` module!
Clean-up test code for polynomial roots.
Refactor and restructure unit tests.
WIP: refactor and restructure tests for Cone, CSG and Ellipse data structures.
Fix typo in method calls and use `lower_case_naming_style`.
Don't use numeric_limits<double>::epsilon().
Add polygon clipping example.
WIP: add unit test for Sutherland-Hodgman polygon clipping.
Specialize `to_std_set` template function for matrices.
Complete the unit test for the general case in polygon intersection.
Merge branch 'maint-test-geometry' of https://github.com/DO-CV/DO-CV into maint-test-geometry
Rename data members of test case and set larger radius search.

FLANN is too imprecise when doing the radius search... One test case still fails in Windows.
Cosmetics.