typescript 3.6 compat fixes

src/apps/viewer/extensions/cellpack/model.ts

src/mol-canvas3d/camera.ts

src/mol-canvas3d/camera/util.ts

src/mol-canvas3d/controls/trackball.ts

src/mol-math/geometry/primitives/sphere3d.ts

src/mol-math/linear-algebra/3d/common.ts

src/mol-math/linear-algebra/3d/mat4.ts

src/mol-math/linear-algebra/3d/quat.ts

src/mol-math/linear-algebra/3d/vec3.ts

src/mol-math/linear-algebra/3d/vec4.ts

src/mol-plugin/layout.ts

src/mol-plugin/state/actions/structure.ts

src/mol-plugin/state/transforms/representation.ts