[misc] Stable support of Mac OS X.

[duburcqa]

• [core] Fix sphere constraint.
• [viewer] 'add_markers' now forward positional arguments.
• [viewer] Fix meshcat port detection on OS X.
• [viewer] Disable physics-based shader is no discrete NVIDIA GPU. ([viewer] Disable physics-based shader is no dedicated GPU. #448)
• [viewer] Improve lighting if no discrete NVIDIA GPU is available.
• [viewer] Force using 'spawn' multiprocessing context for meshcat to avoid crashes on OS X.
• [viewer] It is now possible to interrupt replay without closing viewer.
• [viewer] Fix 'ipykernel' version detection on some setups.
• [simulator] Fix wrong 'viewer.f_external' forces if render without simulation running.
• [misc] Fix import of jiminy if boost is installed on the system but for pinocchio/hppfcl/eigenpy.
• [misc] Fix warnings using 'clang' compilation toolchain.
• [misc] Build shared libs for boost python dependencies on unix to avoid binding issues on OS X and reduce binary size.
• [misc] Enable python unit tests on OSX.
• [misc] Fix jiminy pywrap copied twice in OS X wheels.
• [misc] Build only universal2 wheel on OSX whenever possible.
• [misc] Fix desired chromium version used by pyppeteer being ignored.
• [misc] Update chromium version used by pyppeteer for the latest one available of any platform.
• [misc] Update python dependencies.
• [misc] Fix OS X wheels deployment on Pypi. ([misc] Fix wheel deployement on Pypi. #446)