mol-plugin: custom controls for volume streaming

src/apps/viewer/index.ts

src/mol-plugin/behavior/dynamic/volume-streaming/behavior.ts

src/mol-plugin/index.ts

src/mol-plugin/skin/base/components/controls.scss

src/mol-plugin/ui/controls/common.tsx

src/mol-plugin/ui/custom/volume.tsx

src/mol-plugin/ui/state/apply-action.tsx

src/mol-plugin/ui/state/common.tsx

src/mol-plugin/ui/state/update-transform.tsx