CNC workspace planes and 'P' argument for G2/G3

.travis.yml

Marlin/Configuration_adv.h

Marlin/Marlin_main.cpp

Marlin/enum.h

Marlin/example_configurations/Cartesio/Configuration_adv.h

Marlin/example_configurations/Felix/Configuration_adv.h

...ple_configurations/FolgerTech-i3-2020/Configuration_adv.h

Marlin/example_configurations/Hephestos/Configuration_adv.h

...in/example_configurations/Hephestos_2/Configuration_adv.h

Marlin/example_configurations/K8200/Configuration_adv.h

Marlin/example_configurations/K8400/Configuration_adv.h

Marlin/example_configurations/M150/Configuration_adv.h

Marlin/example_configurations/RigidBot/Configuration_adv.h

Marlin/example_configurations/SCARA/Configuration_adv.h

Marlin/example_configurations/TAZ4/Configuration_adv.h

Marlin/example_configurations/TinyBoy2/Configuration_adv.h

Marlin/example_configurations/WITBOX/Configuration_adv.h

...igurations/delta/FLSUN/auto_calibrate/Configuration_adv.h

...onfigurations/delta/FLSUN/kossel_mini/Configuration_adv.h

.../example_configurations/delta/generic/Configuration_adv.h