input/controls improvements

CHANGELOG.md

src/mol-canvas3d/canvas3d.ts

src/mol-canvas3d/controls/trackball.ts

src/mol-canvas3d/helper/interaction-events.ts

src/mol-plugin/behavior/dynamic/camera.ts

src/mol-plugin/behavior/dynamic/representation.ts

src/mol-plugin/context.ts

src/mol-util/binding.ts

src/mol-util/input/input-observer.ts